// Copyright (c) 2004-2013 Sergey Lyubka
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#if defined(_WIN32)
#if !defined(_CRT_SECURE_NO_WARNINGS)
#define _CRT_SECURE_NO_WARNINGS // Disable deprecation warning in VS2005
#endif
#else
#ifdef __linux__
#define _XOPEN_SOURCE 600     // For flockfile() on Linux
#endif
#define _LARGEFILE_SOURCE     // Enable 64-bit file offsets
#define __STDC_FORMAT_MACROS  // <inttypes.h> wants this for C++
#define __STDC_LIMIT_MACROS   // C++ wants that for INT64_MAX
#endif

#if defined (_MSC_VER)
// conditional expression is constant: introduced by FD_SET(..)
#pragma warning (disable : 4127)
// non-constant aggregate initializer: issued due to missing C99 support
#pragma warning (disable : 4204)
#endif

// Disable WIN32_LEAN_AND_MEAN.
// This makes windows.h always include winsock2.h
#ifdef WIN32_LEAN_AND_MEAN
#undef WIN32_LEAN_AND_MEAN
#endif

#if defined(__SYMBIAN32__)
#define NO_SSL // SSL is not supported
#define NO_CGI // CGI is not supported
#define PATH_MAX FILENAME_MAX
#endif // __SYMBIAN32__

#ifndef _WIN32_WCE // Some ANSI #includes are not available on Windows CE
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#endif // !_WIN32_WCE

#include <time.h>
#include <stdlib.h>
#include <stdarg.h>
#include <assert.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>

#if defined(_WIN32) && !defined(__SYMBIAN32__) // Windows specific
#undef _WIN32_WINNT
#define _WIN32_WINNT 0x0400 // To make it link in VS2005
#include <windows.h>

#ifndef PATH_MAX
#define PATH_MAX MAX_PATH
#endif

#ifndef _WIN32_WCE
#include <process.h>
#include <direct.h>
#include <io.h>
#else // _WIN32_WCE
#define NO_CGI // WinCE has no pipes

typedef long off_t;

#define errno   GetLastError()
#define strerror(x)  _ultoa(x, (char *) _alloca(sizeof(x) *3 ), 10)
#endif // _WIN32_WCE

#define MAKEUQUAD(lo, hi) ((uint64_t)(((uint32_t)(lo)) | \
((uint64_t)((uint32_t)(hi))) << 32))
#define RATE_DIFF 10000000 // 100 nsecs
#define EPOCH_DIFF MAKEUQUAD(0xd53e8000, 0x019db1de)
#define SYS2UNIX_TIME(lo, hi) \
(time_t) ((MAKEUQUAD((lo), (hi)) - EPOCH_DIFF) / RATE_DIFF)

// Visual Studio 6 does not know __func__ or __FUNCTION__
// The rest of MS compilers use __FUNCTION__, not C99 __func__
// Also use _strtoui64 on modern M$ compilers
#if defined(_MSC_VER) && _MSC_VER < 1300
#define STRX(x) #x
#define STR(x) STRX(x)
#define __func__ __FILE__ ":" STR(__LINE__)
#define strtoull(x, y, z) strtoul(x, y, z)
#define strtoll(x, y, z) strtol(x, y, z)
#else
#define __func__  __FUNCTION__
#define strtoull(x, y, z) _strtoui64(x, y, z)
#define strtoll(x, y, z) _strtoi64(x, y, z)
#endif // _MSC_VER

#define ERRNO   GetLastError()
#define NO_SOCKLEN_T
#define SSL_LIB   "ssleay32.dll"
#define CRYPTO_LIB  "libeay32.dll"
#define O_NONBLOCK  0
#if !defined(EWOULDBLOCK)
#define EWOULDBLOCK  WSAEWOULDBLOCK
#endif // !EWOULDBLOCK
#define _POSIX_
#define INT64_FMT  "I64d"

#define WINCDECL __cdecl
#define SHUT_WR 1
#define snprintf _snprintf
#define vsnprintf _vsnprintf
#define mg_sleep(x) Sleep(x)

#define pipe(x) _pipe(x, MG_BUF_LEN, _O_BINARY)
#ifndef popen
#define popen(x, y) _popen(x, y)
#endif
#ifndef pclose
#define pclose(x) _pclose(x)
#endif
#define close(x) _close(x)
#define dlsym(x,y) GetProcAddress((HINSTANCE) (x), (y))
#define RTLD_LAZY  0
#define fseeko(x, y, z) _lseeki64(_fileno(x), (y), (z))
#define fdopen(x, y) _fdopen((x), (y))
#define write(x, y, z) _write((x), (y), (unsigned) z)
#define read(x, y, z) _read((x), (y), (unsigned) z)
#define flockfile(x) EnterCriticalSection(&global_log_file_lock)
#define funlockfile(x) LeaveCriticalSection(&global_log_file_lock)
#define sleep(x) Sleep((x) * 1000)

#if !defined(va_copy)
#define va_copy(x, y) x = y
#endif // !va_copy MINGW #defines va_copy

#if !defined(fileno)
#define fileno(x) _fileno(x)
#endif // !fileno MINGW #defines fileno

typedef HANDLE pthread_mutex_t;
typedef struct {HANDLE signal, broadcast;} pthread_cond_t;
typedef DWORD pthread_t;
#define pid_t HANDLE // MINGW typedefs pid_t to int. Using #define here.

static int pthread_mutex_lock(pthread_mutex_t *);
static int pthread_mutex_unlock(pthread_mutex_t *);
static void to_unicode(const char *path, wchar_t *wbuf, size_t wbuf_len);
struct file;
static char *mg_fgets(char *buf, size_t size, struct file *filep, char **p);

#if defined(HAVE_STDINT)
#include <stdint.h>
#else
typedef unsigned int  uint32_t;
typedef unsigned short  uint16_t;
typedef unsigned __int64 uint64_t;
typedef __int64   int64_t;
#define INT64_MAX  9223372036854775807
#endif // HAVE_STDINT

// POSIX dirent interface
struct dirent {
   char d_name[PATH_MAX];
};

typedef struct DIR {
   HANDLE   handle;
   WIN32_FIND_DATAW info;
   struct dirent  result;
} DIR;

#ifndef HAVE_POLL
struct pollfd {
   int fd;
   short events;
   short revents;
};
#define POLLIN 1
#endif


// Mark required libraries
#ifdef _MSC_VER
#pragma comment(lib, "Ws2_32.lib")
#endif

#else    // UNIX  specific
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/poll.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include <stdint.h>
#include <inttypes.h>
#include <netdb.h>

#include <pwd.h>
#include <unistd.h>
#include <dirent.h>
#if !defined(NO_SSL_DL) && !defined(NO_SSL)
#include <dlfcn.h>
#endif
#include <pthread.h>
#if defined(__MACH__)
#define SSL_LIB   "libssl.dylib"
#define CRYPTO_LIB  "libcrypto.dylib"
#else
#if !defined(SSL_LIB)
#define SSL_LIB   "libssl.so"
#endif
#if !defined(CRYPTO_LIB)
#define CRYPTO_LIB  "libcrypto.so"
#endif
#endif
#ifndef O_BINARY
#define O_BINARY  0
#endif // O_BINARY
#define closesocket(a) close(a)
#define mg_mkdir(x, y) mkdir(x, y)
#define mg_remove(x) remove(x)
#define mg_sleep(x) usleep((x) * 1000)
#define ERRNO errno
#define INVALID_SOCKET (-1)
#define INT64_FMT PRId64
typedef int SOCKET;
#define WINCDECL

#endif // End of Windows and UNIX specific includes

#include "mongoose.h"

#define MONGOOSE_VERSION "3.8"
#define PASSWORDS_FILE_NAME ".htpasswd"
#define CGI_ENVIRONMENT_SIZE 4096
#define MAX_CGI_ENVIR_VARS 64
#define MG_BUF_LEN 8192
#define MAX_REQUEST_SIZE 16384
#define ARRAY_SIZE(array) (sizeof(array) / sizeof(array[0]))

#ifdef _WIN32
static CRITICAL_SECTION global_log_file_lock;
static pthread_t pthread_self(void) {
   return GetCurrentThreadId();
}
#endif // _WIN32

#ifdef DEBUG_TRACE
#undef DEBUG_TRACE
#define DEBUG_TRACE(x)
#else
#if defined(DEBUG)
#define DEBUG_TRACE(x) do { \
flockfile(stdout); \
printf("*** %lu.%p.%s.%d: ", \
(unsigned long) time(NULL), (void *) pthread_self(), \
__func__, __LINE__); \
printf x; \
putchar('\n'); \
fflush(stdout); \
funlockfile(stdout); \
} while (0)
#else
#define DEBUG_TRACE(x)
#endif // DEBUG
#endif // DEBUG_TRACE

// Darwin prior to 7.0 and Win32 do not have socklen_t
#ifdef NO_SOCKLEN_T
typedef int socklen_t;
#endif // NO_SOCKLEN_T
#define _DARWIN_UNLIMITED_SELECT

#if !defined(MSG_NOSIGNAL)
#define MSG_NOSIGNAL 0
#endif

#if !defined(SOMAXCONN)
#define SOMAXCONN 100
#endif

#if !defined(PATH_MAX)
#define PATH_MAX 4096
#endif

static const char *http_500_error = "Internal Server Error";

#if defined(NO_SSL_DL)
#include <openssl/ssl.h>
#else
// SSL loaded dynamically from DLL.
// I put the prototypes here to be independent from OpenSSL source installation.
typedef struct ssl_st SSL;
typedef struct ssl_method_st SSL_METHOD;
typedef struct ssl_ctx_st SSL_CTX;

struct ssl_func {
   const char *name;   // SSL function name
   void  (*ptr)(void); // Function pointer
};

#define SSL_free (* (void (*)(SSL *)) ssl_sw[0].ptr)
#define SSL_accept (* (int (*)(SSL *)) ssl_sw[1].ptr)
#define SSL_connect (* (int (*)(SSL *)) ssl_sw[2].ptr)
#define SSL_read (* (int (*)(SSL *, void *, int)) ssl_sw[3].ptr)
#define SSL_write (* (int (*)(SSL *, const void *,int)) ssl_sw[4].ptr)
#define SSL_get_error (* (int (*)(SSL *, int)) ssl_sw[5].ptr)
#define SSL_set_fd (* (int (*)(SSL *, SOCKET)) ssl_sw[6].ptr)
#define SSL_new (* (SSL * (*)(SSL_CTX *)) ssl_sw[7].ptr)
#define SSL_CTX_new (* (SSL_CTX * (*)(SSL_METHOD *)) ssl_sw[8].ptr)
#define SSLv23_server_method (* (SSL_METHOD * (*)(void)) ssl_sw[9].ptr)
#define SSL_library_init (* (int (*)(void)) ssl_sw[10].ptr)
#define SSL_CTX_use_PrivateKey_file (* (int (*)(SSL_CTX *, \
const char *, int)) ssl_sw[11].ptr)
#define SSL_CTX_use_certificate_file (* (int (*)(SSL_CTX *, \
const char *, int)) ssl_sw[12].ptr)
#define SSL_CTX_set_default_passwd_cb \
(* (void (*)(SSL_CTX *, mg_callback_t)) ssl_sw[13].ptr)
#define SSL_CTX_free (* (void (*)(SSL_CTX *)) ssl_sw[14].ptr)
#define SSL_load_error_strings (* (void (*)(void)) ssl_sw[15].ptr)
#define SSL_CTX_use_certificate_chain_file \
(* (int (*)(SSL_CTX *, const char *)) ssl_sw[16].ptr)
#define SSLv23_client_method (* (SSL_METHOD * (*)(void)) ssl_sw[17].ptr)
#define SSL_pending (* (int (*)(SSL *)) ssl_sw[18].ptr)
#define SSL_CTX_set_verify (* (void (*)(SSL_CTX *, int, int)) ssl_sw[19].ptr)
#define SSL_shutdown (* (int (*)(SSL *)) ssl_sw[20].ptr)

#define CRYPTO_num_locks (* (int (*)(void)) crypto_sw[0].ptr)
#define CRYPTO_set_locking_callback \
(* (void (*)(void (*)(int, int, const char *, int))) crypto_sw[1].ptr)
#define CRYPTO_set_id_callback \
(* (void (*)(unsigned long (*)(void))) crypto_sw[2].ptr)
#define ERR_get_error (* (unsigned long (*)(void)) crypto_sw[3].ptr)
#define ERR_error_string (* (char * (*)(unsigned long,char *)) crypto_sw[4].ptr)

// set_ssl_option() function updates this array.
// It loads SSL library dynamically and changes NULLs to the actual addresses
// of respective functions. The macros above (like SSL_connect()) are really
// just calling these functions indirectly via the pointer.
static struct ssl_func ssl_sw[] = {
   {"SSL_free",   NULL},
   {"SSL_accept",   NULL},
   {"SSL_connect",   NULL},
   {"SSL_read",   NULL},
   {"SSL_write",   NULL},
   {"SSL_get_error",  NULL},
   {"SSL_set_fd",   NULL},
   {"SSL_new",   NULL},
   {"SSL_CTX_new",   NULL},
   {"SSLv23_server_method", NULL},
   {"SSL_library_init",  NULL},
   {"SSL_CTX_use_PrivateKey_file", NULL},
   {"SSL_CTX_use_certificate_file",NULL},
   {"SSL_CTX_set_default_passwd_cb",NULL},
   {"SSL_CTX_free",  NULL},
   {"SSL_load_error_strings", NULL},
   {"SSL_CTX_use_certificate_chain_file", NULL},
   {"SSLv23_client_method", NULL},
   {"SSL_pending", NULL},
   {"SSL_CTX_set_verify", NULL},
   {"SSL_shutdown",   NULL},
   {NULL,    NULL}
};

// Similar array as ssl_sw. These functions could be located in different lib.
#if !defined(NO_SSL)
static struct ssl_func crypto_sw[] = {
   {"CRYPTO_num_locks",  NULL},
   {"CRYPTO_set_locking_callback", NULL},
   {"CRYPTO_set_id_callback", NULL},
   {"ERR_get_error",  NULL},
   {"ERR_error_string", NULL},
   {NULL,    NULL}
};
#endif // NO_SSL
#endif // NO_SSL_DL

static const char *month_names[] = {
   "Jan", "Feb", "Mar", "Apr", "May", "Jun",
   "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};

// Unified socket address. For IPv6 support, add IPv6 address structure
// in the union u.
union usa {
   struct sockaddr sa;
   struct sockaddr_in sin;
#if defined(USE_IPV6)
   struct sockaddr_in6 sin6;
#endif
};

// Describes a string (chunk of memory).
struct vec {
   const char *ptr;
   size_t len;
};

struct file {
   int is_directory;
   time_t modification_time;
   int64_t size;
   FILE *fp;
   const char *membuf;   // Non-NULL if file data is in memory
   // set to 1 if the content is gzipped
   // in which case we need a content-encoding: gzip header
   int gzipped;
};
#define STRUCT_FILE_INITIALIZER {0, 0, 0, NULL, NULL, 0}

// Describes listening socket, or socket which was accept()-ed by the master
// thread and queued for future handling by the worker thread.
struct socket {
   SOCKET sock;          // Listening socket
   union usa lsa;        // Local socket address
   union usa rsa;        // Remote socket address
   unsigned is_ssl:1;    // Is port SSL-ed
   unsigned ssl_redir:1; // Is port supposed to redirect everything to SSL port
};

// NOTE(lsm): this enum shoulds be in sync with the config_options below.
enum {
   CGI_EXTENSIONS, CGI_ENVIRONMENT, PUT_DELETE_PASSWORDS_FILE, CGI_INTERPRETER,
   PROTECT_URI, AUTHENTICATION_DOMAIN, SSI_EXTENSIONS, THROTTLE,
   ACCESS_LOG_FILE, ENABLE_DIRECTORY_LISTING, ERROR_LOG_FILE,
   GLOBAL_PASSWORDS_FILE, INDEX_FILES, ENABLE_KEEP_ALIVE, ACCESS_CONTROL_LIST,
   EXTRA_MIME_TYPES, LISTENING_PORTS, DOCUMENT_ROOT, SSL_CERTIFICATE,
   NUM_THREADS, RUN_AS_USER, REWRITE, HIDE_FILES, REQUEST_TIMEOUT,
   NUM_OPTIONS
};

static const char *config_options[] = {
   "cgi_pattern", "**.cgi$|**.pl$|**.php$",
   "cgi_environment", NULL,
   "put_delete_auth_file", NULL,
   "cgi_interpreter", NULL,
   "protect_uri", NULL,
   "authentication_domain", "mydomain.com",
   "ssi_pattern", "**.shtml$|**.shtm$",
   "throttle", NULL,
   "access_log_file", NULL,
   "enable_directory_listing", "yes",
   "error_log_file", NULL,
   "global_auth_file", NULL,
   "index_files",
   "index.html,index.htm,index.cgi,index.shtml,index.php,index.lp",
   "enable_keep_alive", "no",
   "access_control_list", NULL,
   "extra_mime_types", NULL,
   "listening_ports", "8080",
   "document_root",  ".",
   "ssl_certificate", NULL,
   "num_threads", "50",
   "run_as_user", NULL,
   "url_rewrite_patterns", NULL,
   "hide_files_patterns", NULL,
   "request_timeout_ms", "30000",
   NULL
};

struct mg_context {
   volatile int stop_flag;         // Should we stop event loop
   SSL_CTX *ssl_ctx;               // SSL context
   char *config[NUM_OPTIONS];      // Mongoose configuration parameters
   struct mg_callbacks callbacks;  // User-defined callback function
   void *user_data;                // User-defined data
   
   struct socket *listening_sockets;
   int num_listening_sockets;
   
   volatile int num_threads;  // Number of threads
   pthread_mutex_t mutex;     // Protects (max|num)_threads
   pthread_cond_t  cond;      // Condvar for tracking workers terminations
   
   struct socket queue[20];   // Accepted sockets
   volatile int sq_head;      // Head of the socket queue
   volatile int sq_tail;      // Tail of the socket queue
   pthread_cond_t sq_full;    // Signaled when socket is produced
   pthread_cond_t sq_empty;   // Signaled when socket is consumed
};

struct mg_connection {
   struct mg_request_info request_info;
   struct mg_context *ctx;
   SSL *ssl;                   // SSL descriptor
   SSL_CTX *client_ssl_ctx;    // SSL context for client connections
   struct socket client;       // Connected client
   time_t birth_time;          // Time when request was received
   int64_t num_bytes_sent;     // Total bytes sent to client
   int64_t content_len;        // Content-Length header value
   int64_t consumed_content;   // How many bytes of content have been read
   char *buf;                  // Buffer for received data
   char *path_info;            // PATH_INFO part of the URL
   int must_close;             // 1 if connection must be closed
   int buf_size;               // Buffer size
   int request_len;            // Size of the request + headers in a buffer
   int data_len;               // Total size of data in a buffer
   int status_code;            // HTTP reply status code, e.g. 200
   int throttle;               // Throttling, bytes/sec. <= 0 means no throttle
   time_t last_throttle_time;  // Last time throttled data was sent
   int64_t last_throttle_bytes;// Bytes sent this second
};

// Directory entry
struct de {
   struct mg_connection *conn;
   char *file_name;
   struct file file;
};

const char **mg_get_valid_option_names(void) {
   return config_options;
}

static int is_file_in_memory(struct mg_connection *conn, const char *path,
                             struct file *filep) {
   size_t size = 0;
   if ((filep->membuf = conn->ctx->callbacks.open_file == NULL ? NULL :
        conn->ctx->callbacks.open_file(conn, path, &size)) != NULL) {
      // NOTE: override filep->size only on success. Otherwise, it might break
      // constructs like if (!mg_stat() || !mg_fopen()) ...
      filep->size = size;
   }
   return filep->membuf != NULL;
}

static int is_file_opened(const struct file *filep) {
   return filep->membuf != NULL || filep->fp != NULL;
}

static int mg_fopen(struct mg_connection *conn, const char *path,
                    const char *mode, struct file *filep) {
   if (!is_file_in_memory(conn, path, filep)) {
#ifdef _WIN32
      wchar_t wbuf[PATH_MAX], wmode[20];
      to_unicode(path, wbuf, ARRAY_SIZE(wbuf));
      MultiByteToWideChar(CP_UTF8, 0, mode, -1, wmode, ARRAY_SIZE(wmode));
      filep->fp = _wfopen(wbuf, wmode);
#else
      filep->fp = fopen(path, mode);
#endif
   }
   
   return is_file_opened(filep);
}

static void mg_fclose(struct file *filep) {
   if (filep != NULL && filep->fp != NULL) {
      fclose(filep->fp);
   }
}

static int get_option_index(const char *name) {
   int i;
   
   for (i = 0; config_options[i * 2] != NULL; i++) {
      if (strcmp(config_options[i * 2], name) == 0) {
         return i;
      }
   }
   return -1;
}

const char *mg_get_option(const struct mg_context *ctx, const char *name) {
   int i;
   if ((i = get_option_index(name)) == -1) {
      return NULL;
   } else if (ctx->config[i] == NULL) {
      return "";
   } else {
      return ctx->config[i];
   }
}

static void sockaddr_to_string(char *buf, size_t len,
                               const union usa *usa) {
   buf[0] = '\0';
#if defined(USE_IPV6)
   inet_ntop(usa->sa.sa_family, usa->sa.sa_family == AF_INET ?
             (void *) &usa->sin.sin_addr :
             (void *) &usa->sin6.sin6_addr, buf, len);
#elif defined(_WIN32)
   // Only Windoze Vista (and newer) have inet_ntop()
   strncpy(buf, inet_ntoa(usa->sin.sin_addr), len);
#else
   inet_ntop(usa->sa.sa_family, (void *) &usa->sin.sin_addr, buf, len);
#endif
}

static void cry(struct mg_connection *conn,
                PRINTF_FORMAT_STRING(const char *fmt), ...) PRINTF_ARGS(2, 3);

// Print error message to the opened error log stream.
static void cry(struct mg_connection *conn, const char *fmt, ...) {
   char buf[MG_BUF_LEN], src_addr[20];
   va_list ap;
   FILE *fp;
   time_t timestamp;
   
   va_start(ap, fmt);
   (void) vsnprintf(buf, sizeof(buf), fmt, ap);
   va_end(ap);
   
   // Do not lock when getting the callback value, here and below.
   // I suppose this is fine, since function cannot disappear in the
   // same way string option can.
   if (conn->ctx->callbacks.log_message == NULL ||
       conn->ctx->callbacks.log_message(conn, buf) == 0) {
      fp = conn->ctx == NULL || conn->ctx->config[ERROR_LOG_FILE] == NULL ? NULL :
      fopen(conn->ctx->config[ERROR_LOG_FILE], "a+");
      
      if (fp != NULL) {
         flockfile(fp);
         timestamp = time(NULL);
         
         sockaddr_to_string(src_addr, sizeof(src_addr), &conn->client.rsa);
         fprintf(fp, "[%010lu] [error] [client %s] ", (unsigned long) timestamp,
                 src_addr);
         
         if (conn->request_info.request_method != NULL) {
            fprintf(fp, "%s %s: ", conn->request_info.request_method,
                    conn->request_info.uri);
         }
         
         fprintf(fp, "%s", buf);
         fputc('\n', fp);
         funlockfile(fp);
         fclose(fp);
      }
   }
}

// Return fake connection structure. Used for logging, if connection
// is not applicable at the moment of logging.
static struct mg_connection *fc(struct mg_context *ctx) {
   static struct mg_connection fake_connection;
   fake_connection.ctx = ctx;
   return &fake_connection;
}

const char *mg_version(void) {
   return MONGOOSE_VERSION;
}

struct mg_request_info *mg_get_request_info(struct mg_connection *conn) {
   return &conn->request_info;
}

static void mg_strlcpy(register char *dst, register const char *src, size_t n) {
   for (; *src != '\0' && n > 1; n--) {
      *dst++ = *src++;
   }
   *dst = '\0';
}

static int lowercase(const char *s) {
   return tolower(* (const unsigned char *) s);
}

static int mg_strncasecmp(const char *s1, const char *s2, size_t len) {
   int diff = 0;
   
   if (len > 0)
      do {
         diff = lowercase(s1++) - lowercase(s2++);
      } while (diff == 0 && s1[-1] != '\0' && --len > 0);
   
   return diff;
}

static int mg_strcasecmp(const char *s1, const char *s2) {
   int diff;
   
   do {
      diff = lowercase(s1++) - lowercase(s2++);
   } while (diff == 0 && s1[-1] != '\0');
   
   return diff;
}

static char * mg_strndup(const char *ptr, size_t len) {
   char *p;
   
   if ((p = (char *) malloc(len + 1)) != NULL) {
      mg_strlcpy(p, ptr, len + 1);
   }
   
   return p;
}

static char * mg_strdup(const char *str) {
   return mg_strndup(str, strlen(str));
}

static const char *mg_strcasestr(const char *big_str, const char *small_str) {
   int i, big_len = strlen(big_str), small_len = strlen(small_str);
   
   for (i = 0; i <= big_len - small_len; i++) {
      if (mg_strncasecmp(big_str + i, small_str, small_len) == 0) {
         return big_str + i;
      }
   }
   
   return NULL;
}

// Like snprintf(), but never returns negative value, or a value
// that is larger than a supplied buffer.
// Thanks to Adam Zeldis to pointing snprintf()-caused vulnerability
// in his audit report.
static int mg_vsnprintf(struct mg_connection *conn, char *buf, size_t buflen,
                        const char *fmt, va_list ap) {
   int n;
   
   if (buflen == 0)
      return 0;
   
   n = vsnprintf(buf, buflen, fmt, ap);
   
   if (n < 0) {
      cry(conn, "vsnprintf error");
      n = 0;
   } else if (n >= (int) buflen) {
      cry(conn, "truncating vsnprintf buffer: [%.*s]",
          n > 200 ? 200 : n, buf);
      n = (int) buflen - 1;
   }
   buf[n] = '\0';
   
   return n;
}

static int mg_snprintf(struct mg_connection *conn, char *buf, size_t buflen,
                       PRINTF_FORMAT_STRING(const char *fmt), ...)
PRINTF_ARGS(4, 5);

static int mg_snprintf(struct mg_connection *conn, char *buf, size_t buflen,
                       const char *fmt, ...) {
   va_list ap;
   int n;
   
   va_start(ap, fmt);
   n = mg_vsnprintf(conn, buf, buflen, fmt, ap);
   va_end(ap);
   
   return n;
}

// Skip the characters until one of the delimiters characters found.
// 0-terminate resulting word. Skip the delimiter and following whitespaces.
// Advance pointer to buffer to the next word. Return found 0-terminated word.
// Delimiters can be quoted with quotechar.
static char *skip_quoted(char **buf, const char *delimiters,
                         const char *whitespace, char quotechar) {
   char *p, *begin_word, *end_word, *end_whitespace;
   
   begin_word = *buf;
   end_word = begin_word + strcspn(begin_word, delimiters);
   
   // Check for quotechar
   if (end_word > begin_word) {
      p = end_word - 1;
      while (*p == quotechar) {
         // If there is anything beyond end_word, copy it
         if (*end_word == '\0') {
            *p = '\0';
            break;
         } else {
            size_t end_off = strcspn(end_word + 1, delimiters);
            memmove (p, end_word, end_off + 1);
            p += end_off; // p must correspond to end_word - 1
            end_word += end_off + 1;
         }
      }
      for (p++; p < end_word; p++) {
         *p = '\0';
      }
   }
   
   if (*end_word == '\0') {
      *buf = end_word;
   } else {
      end_whitespace = end_word + 1 + strspn(end_word + 1, whitespace);
      
      for (p = end_word; p < end_whitespace; p++) {
         *p = '\0';
      }
      
      *buf = end_whitespace;
   }
   
   return begin_word;
}

// Simplified version of skip_quoted without quote char
// and whitespace == delimiters
static char *skip(char **buf, const char *delimiters) {
   return skip_quoted(buf, delimiters, delimiters, 0);
}


// Return HTTP header value, or NULL if not found.
static const char *get_header(const struct mg_request_info *ri,
                              const char *name) {
   int i;
   
   for (i = 0; i < ri->num_headers; i++)
      if (!mg_strcasecmp(name, ri->http_headers[i].name))
         return ri->http_headers[i].value;
   
   return NULL;
}

const char *mg_get_header(const struct mg_connection *conn, const char *name) {
   return get_header(&conn->request_info, name);
}

// A helper function for traversing a comma separated list of values.
// It returns a list pointer shifted to the next value, or NULL if the end
// of the list found.
// Value is stored in val vector. If value has form "x=y", then eq_val
// vector is initialized to point to the "y" part, and val vector length
// is adjusted to point only to "x".
static const char *next_option(const char *list, struct vec *val,
                               struct vec *eq_val) {
   if (list == NULL || *list == '\0') {
      // End of the list
      list = NULL;
   } else {
      val->ptr = list;
      if ((list = strchr(val->ptr, ',')) != NULL) {
         // Comma found. Store length and shift the list ptr
         val->len = list - val->ptr;
         list++;
      } else {
         // This value is the last one
         list = val->ptr + strlen(val->ptr);
         val->len = list - val->ptr;
      }
      
      if (eq_val != NULL) {
         // Value has form "x=y", adjust pointers and lengths
         // so that val points to "x", and eq_val points to "y".
         eq_val->len = 0;
         eq_val->ptr = (const char *) memchr(val->ptr, '=', val->len);
         if (eq_val->ptr != NULL) {
            eq_val->ptr++;  // Skip over '=' character
            eq_val->len = val->ptr + val->len - eq_val->ptr;
            val->len = (eq_val->ptr - val->ptr) - 1;
         }
      }
   }
   
   return list;
}

static int match_prefix(const char *pattern, int pattern_len, const char *str) {
   const char *or_str;
   int i, j, len, res;
   
   if ((or_str = (const char *) memchr(pattern, '|', pattern_len)) != NULL) {
      res = match_prefix(pattern, or_str - pattern, str);
      return res > 0 ? res :
      match_prefix(or_str + 1, (pattern + pattern_len) - (or_str + 1), str);
   }
   
   i = j = 0;
   res = -1;
   for (; i < pattern_len; i++, j++) {
      if (pattern[i] == '?' && str[j] != '\0') {
         continue;
      } else if (pattern[i] == '$') {
         return str[j] == '\0' ? j : -1;
      } else if (pattern[i] == '*') {
         i++;
         if (pattern[i] == '*') {
            i++;
            len = (int) strlen(str + j);
         } else {
            len = (int) strcspn(str + j, "/");
         }
         if (i == pattern_len) {
            return j + len;
         }
         do {
            res = match_prefix(pattern + i, pattern_len - i, str + j + len);
         } while (res == -1 && len-- > 0);
         return res == -1 ? -1 : j + res + len;
      } else if (pattern[i] != str[j]) {
         return -1;
      }
   }
   return j;
}

// HTTP 1.1 assumes keep alive if "Connection:" header is not set
// This function must tolerate situations when connection info is not
// set up, for example if request parsing failed.
static int should_keep_alive(const struct mg_connection *conn) {
   const char *http_version = conn->request_info.http_version;
   const char *header = mg_get_header(conn, "Connection");
   if (conn->must_close ||
       conn->status_code == 401 ||
       mg_strcasecmp(conn->ctx->config[ENABLE_KEEP_ALIVE], "yes") != 0 ||
       (header != NULL && mg_strcasecmp(header, "keep-alive") != 0) ||
       (header == NULL && http_version && strcmp(http_version, "1.1"))) {
      return 0;
   }
   return 1;
}

static const char *suggest_connection_header(const struct mg_connection *conn) {
   return should_keep_alive(conn) ? "keep-alive" : "close";
}

static void send_http_error(struct mg_connection *, int, const char *,
                            PRINTF_FORMAT_STRING(const char *fmt), ...)
PRINTF_ARGS(4, 5);


static void send_http_error(struct mg_connection *conn, int status,
                            const char *reason, const char *fmt, ...) {
   char buf[MG_BUF_LEN];
   va_list ap;
   int len = 0;
   
   conn->status_code = status;
   if (conn->ctx->callbacks.http_error == NULL ||
       conn->ctx->callbacks.http_error(conn, status)) {
      buf[0] = '\0';
      
      // Errors 1xx, 204 and 304 MUST NOT send a body
      if (status > 199 && status != 204 && status != 304) {
         len = mg_snprintf(conn, buf, sizeof(buf), "Error %d: %s", status, reason);
         buf[len++] = '\n';
         
         va_start(ap, fmt);
         len += mg_vsnprintf(conn, buf + len, sizeof(buf) - len, fmt, ap);
         va_end(ap);
      }
      DEBUG_TRACE(("[%s]", buf));
      
      mg_printf(conn, "HTTP/1.1 %d %s\r\n"
                "Content-Length: %d\r\n"
                "Connection: %s\r\n\r\n", status, reason, len,
                suggest_connection_header(conn));
      conn->num_bytes_sent += mg_printf(conn, "%s", buf);
   }
}

#if defined(_WIN32) && !defined(__SYMBIAN32__)
static int pthread_mutex_init(pthread_mutex_t *mutex, void *unused) {
   (void) unused;
   *mutex = CreateMutex(NULL, FALSE, NULL);
   return *mutex == NULL ? -1 : 0;
}

static int pthread_mutex_destroy(pthread_mutex_t *mutex) {
   return CloseHandle(*mutex) == 0 ? -1 : 0;
}

static int pthread_mutex_lock(pthread_mutex_t *mutex) {
   return WaitForSingleObject(*mutex, INFINITE) == WAIT_OBJECT_0? 0 : -1;
}

static int pthread_mutex_unlock(pthread_mutex_t *mutex) {
   return ReleaseMutex(*mutex) == 0 ? -1 : 0;
}

static int pthread_cond_init(pthread_cond_t *cv, const void *unused) {
   (void) unused;
   cv->signal = CreateEvent(NULL, FALSE, FALSE, NULL);
   cv->broadcast = CreateEvent(NULL, TRUE, FALSE, NULL);
   return cv->signal != NULL && cv->broadcast != NULL ? 0 : -1;
}

static int pthread_cond_wait(pthread_cond_t *cv, pthread_mutex_t *mutex) {
   HANDLE handles[] = {cv->signal, cv->broadcast};
   ReleaseMutex(*mutex);
   WaitForMultipleObjects(2, handles, FALSE, INFINITE);
   return WaitForSingleObject(*mutex, INFINITE) == WAIT_OBJECT_0? 0 : -1;
}

static int pthread_cond_signal(pthread_cond_t *cv) {
   return SetEvent(cv->signal) == 0 ? -1 : 0;
}

static int pthread_cond_broadcast(pthread_cond_t *cv) {
   // Implementation with PulseEvent() has race condition, see
   // http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
   return PulseEvent(cv->broadcast) == 0 ? -1 : 0;
}

static int pthread_cond_destroy(pthread_cond_t *cv) {
   return CloseHandle(cv->signal) && CloseHandle(cv->broadcast) ? 0 : -1;
}

// For Windows, change all slashes to backslashes in path names.
static void change_slashes_to_backslashes(char *path) {
   int i;
   
   for (i = 0; path[i] != '\0'; i++) {
      if (path[i] == '/')
         path[i] = '\\';
      // i > 0 check is to preserve UNC paths, like \\server\file.txt
      if (path[i] == '\\' && i > 0)
         while (path[i + 1] == '\\' || path[i + 1] == '/')
            (void) memmove(path + i + 1,
                           path + i + 2, strlen(path + i + 1));
   }
}

// Encode 'path' which is assumed UTF-8 string, into UNICODE string.
// wbuf and wbuf_len is a target buffer and its length.
static void to_unicode(const char *path, wchar_t *wbuf, size_t wbuf_len) {
   char buf[PATH_MAX], buf2[PATH_MAX];
   
   mg_strlcpy(buf, path, sizeof(buf));
   change_slashes_to_backslashes(buf);
   
   // Convert to Unicode and back. If doubly-converted string does not
   // match the original, something is fishy, reject.
   memset(wbuf, 0, wbuf_len * sizeof(wchar_t));
   MultiByteToWideChar(CP_UTF8, 0, buf, -1, wbuf, (int) wbuf_len);
   WideCharToMultiByte(CP_UTF8, 0, wbuf, (int) wbuf_len, buf2, sizeof(buf2),
                       NULL, NULL);
   if (strcmp(buf, buf2) != 0) {
      wbuf[0] = L'\0';
   }
}

#if defined(_WIN32_WCE)
static time_t time(time_t *ptime) {
   time_t t;
   SYSTEMTIME st;
   FILETIME ft;
   
   GetSystemTime(&st);
   SystemTimeToFileTime(&st, &ft);
   t = SYS2UNIX_TIME(ft.dwLowDateTime, ft.dwHighDateTime);
   
   if (ptime != NULL) {
      *ptime = t;
   }
   
   return t;
}

static struct tm *localtime(const time_t *ptime, struct tm *ptm) {
   int64_t t = ((int64_t) *ptime) * RATE_DIFF + EPOCH_DIFF;
   FILETIME ft, lft;
   SYSTEMTIME st;
   TIME_ZONE_INFORMATION tzinfo;
   
   if (ptm == NULL) {
      return NULL;
   }
   
   * (int64_t *) &ft = t;
   FileTimeToLocalFileTime(&ft, &lft);
   FileTimeToSystemTime(&lft, &st);
   ptm->tm_year = st.wYear - 1900;
   ptm->tm_mon = st.wMonth - 1;
   ptm->tm_wday = st.wDayOfWeek;
   ptm->tm_mday = st.wDay;
   ptm->tm_hour = st.wHour;
   ptm->tm_min = st.wMinute;
   ptm->tm_sec = st.wSecond;
   ptm->tm_yday = 0; // hope nobody uses this
   ptm->tm_isdst =
   GetTimeZoneInformation(&tzinfo) == TIME_ZONE_ID_DAYLIGHT ? 1 : 0;
   
   return ptm;
}

static struct tm *gmtime(const time_t *ptime, struct tm *ptm) {
   // FIXME(lsm): fix this.
   return localtime(ptime, ptm);
}

static size_t strftime(char *dst, size_t dst_size, const char *fmt,
                       const struct tm *tm) {
   (void) snprintf(dst, dst_size, "implement strftime() for WinCE");
   return 0;
}
#endif

// Windows happily opens files with some garbage at the end of file name.
// For example, fopen("a.cgi    ", "r") on Windows successfully opens
// "a.cgi", despite one would expect an error back.
// This function returns non-0 if path ends with some garbage.
static int path_cannot_disclose_cgi(const char *path) {
   static const char *allowed_last_characters = "_-";
   int last = path[strlen(path) - 1];
   return isalnum(last) || strchr(allowed_last_characters, last) != NULL;
}

static int mg_stat(struct mg_connection *conn, const char *path,
                   struct file *filep) {
   wchar_t wbuf[PATH_MAX];
   WIN32_FILE_ATTRIBUTE_DATA info;
   
   if (!is_file_in_memory(conn, path, filep)) {
      to_unicode(path, wbuf, ARRAY_SIZE(wbuf));
      if (GetFileAttributesExW(wbuf, GetFileExInfoStandard, &info) != 0) {
         filep->size = MAKEUQUAD(info.nFileSizeLow, info.nFileSizeHigh);
         filep->modification_time = SYS2UNIX_TIME(
                                                  info.ftLastWriteTime.dwLowDateTime,
                                                  info.ftLastWriteTime.dwHighDateTime);
         filep->is_directory = info.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY;
         // If file name is fishy, reset the file structure and return error.
         // Note it is important to reset, not just return the error, cause
         // functions like is_file_opened() check the struct.
         if (!filep->is_directory && !path_cannot_disclose_cgi(path)) {
            memset(filep, 0, sizeof(*filep));
         }
      }
   }
   
   return filep->membuf != NULL || filep->modification_time != 0;
}

static int mg_remove(const char *path) {
   wchar_t wbuf[PATH_MAX];
   to_unicode(path, wbuf, ARRAY_SIZE(wbuf));
   return DeleteFileW(wbuf) ? 0 : -1;
}

static int mg_mkdir(const char *path, int mode) {
   char buf[PATH_MAX];
   wchar_t wbuf[PATH_MAX];
   
   (void) mode;
   mg_strlcpy(buf, path, sizeof(buf));
   change_slashes_to_backslashes(buf);
   
   (void) MultiByteToWideChar(CP_UTF8, 0, buf, -1, wbuf, ARRAY_SIZE(wbuf));
   
   return CreateDirectoryW(wbuf, NULL) ? 0 : -1;
}

// Implementation of POSIX opendir/closedir/readdir for Windows.
static DIR * opendir(const char *name) {
   DIR *dir = NULL;
   wchar_t wpath[PATH_MAX];
   DWORD attrs;
   
   if (name == NULL) {
      SetLastError(ERROR_BAD_ARGUMENTS);
   } else if ((dir = (DIR *) malloc(sizeof(*dir))) == NULL) {
      SetLastError(ERROR_NOT_ENOUGH_MEMORY);
   } else {
      to_unicode(name, wpath, ARRAY_SIZE(wpath));
      attrs = GetFileAttributesW(wpath);
      if (attrs != 0xFFFFFFFF &&
          ((attrs & FILE_ATTRIBUTE_DIRECTORY) == FILE_ATTRIBUTE_DIRECTORY)) {
         (void) wcscat(wpath, L"\\*");
         dir->handle = FindFirstFileW(wpath, &dir->info);
         dir->result.d_name[0] = '\0';
      } else {
         free(dir);
         dir = NULL;
      }
   }
   
   return dir;
}

static int closedir(DIR *dir) {
   int result = 0;
   
   if (dir != NULL) {
      if (dir->handle != INVALID_HANDLE_VALUE)
         result = FindClose(dir->handle) ? 0 : -1;
      
      free(dir);
   } else {
      result = -1;
      SetLastError(ERROR_BAD_ARGUMENTS);
   }
   
   return result;
}

static struct dirent *readdir(DIR *dir) {
   struct dirent *result = 0;
   
   if (dir) {
      if (dir->handle != INVALID_HANDLE_VALUE) {
         result = &dir->result;
         (void) WideCharToMultiByte(CP_UTF8, 0,
                                    dir->info.cFileName, -1, result->d_name,
                                    sizeof(result->d_name), NULL, NULL);
         
         if (!FindNextFileW(dir->handle, &dir->info)) {
            (void) FindClose(dir->handle);
            dir->handle = INVALID_HANDLE_VALUE;
         }
         
      } else {
         SetLastError(ERROR_FILE_NOT_FOUND);
      }
   } else {
      SetLastError(ERROR_BAD_ARGUMENTS);
   }
   
   return result;
}

#ifndef HAVE_POLL
static int poll(struct pollfd *pfd, int n, int milliseconds) {
   struct timeval tv;
   fd_set set;
   int i, result, maxfd = 0;
   
   tv.tv_sec = milliseconds / 1000;
   tv.tv_usec = (milliseconds % 1000) * 1000;
   FD_ZERO(&set);
   
   for (i = 0; i < n; i++) {
      FD_SET((SOCKET) pfd[i].fd, &set);
      pfd[i].revents = 0;
      
      if (pfd[i].fd > maxfd) {
         maxfd = pfd[i].fd;
      }
   }
   
   if ((result = select(maxfd + 1, &set, NULL, NULL, &tv)) > 0) {
      for (i = 0; i < n; i++) {
         if (FD_ISSET(pfd[i].fd, &set)) {
            pfd[i].revents = POLLIN;
         }
      }
   }
   
   return result;
}
#endif // HAVE_POLL

#define set_close_on_exec(x) // No FD_CLOEXEC on Windows

int mg_start_thread(mg_thread_func_t f, void *p) {
   return (long)_beginthread((void (__cdecl *)(void *)) f, 0, p) == -1L ? -1 : 0;
}

static HANDLE dlopen(const char *dll_name, int flags) {
   wchar_t wbuf[PATH_MAX];
   (void) flags;
   to_unicode(dll_name, wbuf, ARRAY_SIZE(wbuf));
   return LoadLibraryW(wbuf);
}

#if !defined(NO_CGI)
#define SIGKILL 0
static int kill(pid_t pid, int sig_num) {
   (void) TerminateProcess(pid, sig_num);
   (void) CloseHandle(pid);
   return 0;
}

static void trim_trailing_whitespaces(char *s) {
   char *e = s + strlen(s) - 1;
   while (e > s && isspace(* (unsigned char *) e)) {
      *e-- = '\0';
   }
}

static pid_t spawn_process(struct mg_connection *conn, const char *prog,
                           char *envblk, char *envp[], int fd_stdin,
                           int fd_stdout, const char *dir) {
   HANDLE me;
   char *p, *interp, full_interp[PATH_MAX], full_dir[PATH_MAX],
   cmdline[PATH_MAX], buf[PATH_MAX];
   struct file file = STRUCT_FILE_INITIALIZER;
   STARTUPINFOA si;
   PROCESS_INFORMATION pi = { 0 };
   
   (void) envp;
   
   memset(&si, 0, sizeof(si));
   si.cb = sizeof(si);
   
   // TODO(lsm): redirect CGI errors to the error log file
   si.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
   si.wShowWindow = SW_HIDE;
   
   me = GetCurrentProcess();
   DuplicateHandle(me, (HANDLE) _get_osfhandle(fd_stdin), me,
                   &si.hStdInput, 0, TRUE, DUPLICATE_SAME_ACCESS);
   DuplicateHandle(me, (HANDLE) _get_osfhandle(fd_stdout), me,
                   &si.hStdOutput, 0, TRUE, DUPLICATE_SAME_ACCESS);
   
   // If CGI file is a script, try to read the interpreter line
   interp = conn->ctx->config[CGI_INTERPRETER];
   if (interp == NULL) {
      buf[0] = buf[1] = '\0';
      
      // Read the first line of the script into the buffer
      snprintf(cmdline, sizeof(cmdline), "%s%c%s", dir, '/', prog);
      if (mg_fopen(conn, cmdline, "r", &file)) {
         p = (char *) file.membuf;
         mg_fgets(buf, sizeof(buf), &file, &p);
         mg_fclose(&file);
         buf[sizeof(buf) - 1] = '\0';
      }
      
      if (buf[0] == '#' && buf[1] == '!') {
         trim_trailing_whitespaces(buf + 2);
      } else {
         buf[2] = '\0';
      }
      interp = buf + 2;
   }
   
   if (interp[0] != '\0') {
      GetFullPathNameA(interp, sizeof(full_interp), full_interp, NULL);
      interp = full_interp;
   }
   GetFullPathNameA(dir, sizeof(full_dir), full_dir, NULL);
   
   mg_snprintf(conn, cmdline, sizeof(cmdline), "%s%s%s\\%s",
               interp, interp[0] == '\0' ? "" : " ", full_dir, prog);
   
   DEBUG_TRACE(("Running [%s]", cmdline));
   if (CreateProcessA(NULL, cmdline, NULL, NULL, TRUE,
                      CREATE_NEW_PROCESS_GROUP, envblk, NULL, &si, &pi) == 0) {
      cry(conn, "%s: CreateProcess(%s): %ld",
          __func__, cmdline, ERRNO);
      pi.hProcess = (pid_t) -1;
   }
   
   // Always close these to prevent handle leakage.
   (void) close(fd_stdin);
   (void) close(fd_stdout);
   
   (void) CloseHandle(si.hStdOutput);
   (void) CloseHandle(si.hStdInput);
   (void) CloseHandle(pi.hThread);
   
   return (pid_t) pi.hProcess;
}
#endif // !NO_CGI

static int set_non_blocking_mode(SOCKET sock) {
   unsigned long on = 1;
   return ioctlsocket(sock, FIONBIO, &on);
}

#else
static int mg_stat(struct mg_connection *conn, const char *path,
                   struct file *filep) {
   struct stat st;
   
   if (!is_file_in_memory(conn, path, filep) && !stat(path, &st)) {
      filep->size = st.st_size;
      filep->modification_time = st.st_mtime;
      filep->is_directory = S_ISDIR(st.st_mode);
   } else {
      filep->modification_time = (time_t) 0;
   }
   
   return filep->membuf != NULL || filep->modification_time != (time_t) 0;
}

static void set_close_on_exec(int fd) {
   fcntl(fd, F_SETFD, FD_CLOEXEC);
}

int mg_start_thread(mg_thread_func_t func, void *param) {
   pthread_t thread_id;
   pthread_attr_t attr;
   int result;
   
   (void) pthread_attr_init(&attr);
   (void) pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
   // TODO(lsm): figure out why mongoose dies on Linux if next line is enabled
   // (void) pthread_attr_setstacksize(&attr, sizeof(struct mg_connection) * 5);
   
   result = pthread_create(&thread_id, &attr, func, param);
   pthread_attr_destroy(&attr);
   
   return result;
}

#ifndef NO_CGI
static pid_t spawn_process(struct mg_connection *conn, const char *prog,
                           char *envblk, char *envp[], int fd_stdin,
                           int fd_stdout, const char *dir) {
   pid_t pid;
   const char *interp;
   
   (void) envblk;
   
   if ((pid = fork()) == -1) {
      // Parent
      send_http_error(conn, 500, http_500_error, "fork(): %s", strerror(ERRNO));
   } else if (pid == 0) {
      // Child
      if (chdir(dir) != 0) {
         cry(conn, "%s: chdir(%s): %s", __func__, dir, strerror(ERRNO));
      } else if (dup2(fd_stdin, 0) == -1) {
         cry(conn, "%s: dup2(%d, 0): %s", __func__, fd_stdin, strerror(ERRNO));
      } else if (dup2(fd_stdout, 1) == -1) {
         cry(conn, "%s: dup2(%d, 1): %s", __func__, fd_stdout, strerror(ERRNO));
      } else {
         (void) dup2(fd_stdout, 2);
         (void) close(fd_stdin);
         (void) close(fd_stdout);
         
         // After exec, all signal handlers are restored to their default values,
         // with one exception of SIGCHLD. According to POSIX.1-2001 and Linux's
         // implementation, SIGCHLD's handler will leave unchanged after exec
         // if it was set to be ignored. Restore it to default action.
         signal(SIGCHLD, SIG_DFL);
         
         interp = conn->ctx->config[CGI_INTERPRETER];
         if (interp == NULL) {
            (void) execle(prog, prog, NULL, envp);
            cry(conn, "%s: execle(%s): %s", __func__, prog, strerror(ERRNO));
         } else {
            (void) execle(interp, interp, prog, NULL, envp);
            cry(conn, "%s: execle(%s %s): %s", __func__, interp, prog,
                strerror(ERRNO));
         }
      }
      exit(EXIT_FAILURE);
   }
   
   // Parent. Close stdio descriptors
   (void) close(fd_stdin);
   (void) close(fd_stdout);
   
   return pid;
}
#endif // !NO_CGI

static int set_non_blocking_mode(SOCKET sock) {
   int flags;
   
   flags = fcntl(sock, F_GETFL, 0);
   (void) fcntl(sock, F_SETFL, flags | O_NONBLOCK);
   
   return 0;
}
#endif // _WIN32

// Write data to the IO channel - opened file descriptor, socket or SSL
// descriptor. Return number of bytes written.
static int64_t push(FILE *fp, SOCKET sock, SSL *ssl, const char *buf,
                    int64_t len) {
   int64_t sent;
   int n, k;
   
   (void) ssl;  // Get rid of warning
   sent = 0;
   while (sent < len) {
      
      // How many bytes we send in this iteration
      k = len - sent > INT_MAX ? INT_MAX : (int) (len - sent);
      
#ifndef NO_SSL
      if (ssl != NULL) {
         n = SSL_write(ssl, buf + sent, k);
      } else
#endif
         if (fp != NULL) {
            n = (int) fwrite(buf + sent, 1, (size_t) k, fp);
            if (ferror(fp))
               n = -1;
         } else {
            n = send(sock, buf + sent, (size_t) k, MSG_NOSIGNAL);
         }
      
      if (n <= 0)
         break;
      
      sent += n;
   }
   
   return sent;
}

// Read from IO channel - opened file descriptor, socket, or SSL descriptor.
// Return negative value on error, or number of bytes read on success.
static int pull(FILE *fp, struct mg_connection *conn, char *buf, int len) {
   int nread;
   
   if (fp != NULL) {
      // Use read() instead of fread(), because if we're reading from the CGI
      // pipe, fread() may block until IO buffer is filled up. We cannot afford
      // to block and must pass all read bytes immediately to the client.
      nread = read(fileno(fp), buf, (size_t) len);
#ifndef NO_SSL
   } else if (conn->ssl != NULL) {
      nread = SSL_read(conn->ssl, buf, len);
#endif
   } else {
      nread = recv(conn->client.sock, buf, (size_t) len, 0);
   }
   
   return conn->ctx->stop_flag ? -1 : nread;
}

static int pull_all(FILE *fp, struct mg_connection *conn, char *buf, int len) {
   int n, nread = 0;
   
   while (len > 0) {
      n = pull(fp, conn, buf + nread, len);
      if (n < 0) {
         nread = n;  // Propagate the error
         break;
      } else if (n == 0) {
         break;  // No more data to read
      } else {
         conn->consumed_content += n;
         nread += n;
         len -= n;
      }
   }
   
   return nread;
}

int mg_read(struct mg_connection *conn, void *buf, size_t len) {
   int n, buffered_len, nread;
   const char *body;
   
   nread = 0;
   if (conn->consumed_content < conn->content_len) {
      // Adjust number of bytes to read.
      int64_t to_read = conn->content_len - conn->consumed_content;
      if (to_read < (int64_t) len) {
         len = (size_t) to_read;
      }
      
      // Return buffered data
      body = conn->buf + conn->request_len + conn->consumed_content;
      buffered_len = &conn->buf[conn->data_len] - body;
      if (buffered_len > 0) {
         if (len < (size_t) buffered_len) {
            buffered_len = (int) len;
         }
         memcpy(buf, body, (size_t) buffered_len);
         len -= buffered_len;
         conn->consumed_content += buffered_len;
         nread += buffered_len;
         buf = (char *) buf + buffered_len;
      }
      
      // We have returned all buffered data. Read new data from the remote socket.
      n = pull_all(NULL, conn, (char *) buf, (int) len);
      nread = n >= 0 ? nread + n : n;
   }
   return nread;
}

int mg_write(struct mg_connection *conn, const void *buf, size_t len) {
   time_t now;
   int64_t n, total, allowed;
   
   if (conn->throttle > 0) {
      if ((now = time(NULL)) != conn->last_throttle_time) {
         conn->last_throttle_time = now;
         conn->last_throttle_bytes = 0;
      }
      allowed = conn->throttle - conn->last_throttle_bytes;
      if (allowed > (int64_t) len) {
         allowed = len;
      }
      if ((total = push(NULL, conn->client.sock, conn->ssl, (const char *) buf,
                        (int64_t) allowed)) == allowed) {
         buf = (char *) buf + total;
         conn->last_throttle_bytes += total;
         while (total < (int64_t) len && conn->ctx->stop_flag == 0) {
            allowed = conn->throttle > (int64_t) len - total ?
            (int64_t) len - total : conn->throttle;
            if ((n = push(NULL, conn->client.sock, conn->ssl, (const char *) buf,
                          (int64_t) allowed)) != allowed) {
               break;
            }
            sleep(1);
            conn->last_throttle_bytes = allowed;
            conn->last_throttle_time = time(NULL);
            buf = (char *) buf + n;
            total += n;
         }
      }
   } else {
      total = push(NULL, conn->client.sock, conn->ssl, (const char *) buf,
                   (int64_t) len);
   }
   return (int) total;
}

// Print message to buffer. If buffer is large enough to hold the message,
// return buffer. If buffer is to small, allocate large enough buffer on heap,
// and return allocated buffer.
static int alloc_vprintf(char **buf, size_t size, const char *fmt, va_list ap) {
   va_list ap_copy;
   int len;
   
   // Windows is not standard-compliant, and vsnprintf() returns -1 if
   // buffer is too small. Also, older versions of msvcrt.dll do not have
   // _vscprintf().  However, if size is 0, vsnprintf() behaves correctly.
   // Therefore, we make two passes: on first pass, get required message length.
   // On second pass, actually print the message.
   va_copy(ap_copy, ap);
   len = vsnprintf(NULL, 0, fmt, ap_copy);
   
   if (len > (int) size &&
       (size = len + 1) > 0 &&
       (*buf = (char *) malloc(size)) == NULL) {
      len = -1;  // Allocation failed, mark failure
   } else {
      va_copy(ap_copy, ap);
      vsnprintf(*buf, size, fmt, ap_copy);
   }
   
   return len;
}

int mg_vprintf(struct mg_connection *conn, const char *fmt, va_list ap) {
   char mem[MG_BUF_LEN], *buf = mem;
   int len;
   
   if ((len = alloc_vprintf(&buf, sizeof(mem), fmt, ap)) > 0) {
      len = mg_write(conn, buf, (size_t) len);
   }
   if (buf != mem && buf != NULL) {
      free(buf);
   }
   
   return len;
}

int mg_printf(struct mg_connection *conn, const char *fmt, ...) {
   va_list ap;
   va_start(ap, fmt);
   return mg_vprintf(conn, fmt, ap);
}

int mg_url_decode(const char *src, int src_len, char *dst,
                  int dst_len, int is_form_url_encoded) {
   int i, j, a, b;
#define HEXTOI(x) (isdigit(x) ? x - '0' : x - 'W')
   
   for (i = j = 0; i < src_len && j < dst_len - 1; i++, j++) {
      if (src[i] == '%' && i < src_len - 2 &&
          isxdigit(* (const unsigned char *) (src + i + 1)) &&
          isxdigit(* (const unsigned char *) (src + i + 2))) {
         a = tolower(* (const unsigned char *) (src + i + 1));
         b = tolower(* (const unsigned char *) (src + i + 2));
         dst[j] = (char) ((HEXTOI(a) << 4) | HEXTOI(b));
         i += 2;
      } else if (is_form_url_encoded && src[i] == '+') {
         dst[j] = ' ';
      } else {
         dst[j] = src[i];
      }
   }
   
   dst[j] = '\0'; // Null-terminate the destination
   
   return i >= src_len ? j : -1;
}

int mg_get_var(const char *data, size_t data_len, const char *name,
               char *dst, size_t dst_len) {
   const char *p, *e, *s;
   size_t name_len;
   int len;
   
   if (dst == NULL || dst_len == 0) {
      len = -2;
   } else if (data == NULL || name == NULL || data_len == 0) {
      len = -1;
      dst[0] = '\0';
   } else {
      name_len = strlen(name);
      e = data + data_len;
      len = -1;
      dst[0] = '\0';
      
      // data is "var1=val1&var2=val2...". Find variable first
      for (p = data; p + name_len < e; p++) {
         if ((p == data || p[-1] == '&') && p[name_len] == '=' &&
             !mg_strncasecmp(name, p, name_len)) {
            
            // Point p to variable value
            p += name_len + 1;
            
            // Point s to the end of the value
            s = (const char *) memchr(p, '&', (size_t)(e - p));
            if (s == NULL) {
               s = e;
            }
            assert(s >= p);
            
            // Decode variable into destination buffer
            len = mg_url_decode(p, (size_t)(s - p), dst, dst_len, 1);
            
            // Redirect error code from -1 to -2 (destination buffer too small).
            if (len == -1) {
               len = -2;
            }
            break;
         }
      }
   }
   
   return len;
}

int mg_get_cookie(const char *cookie_header, const char *var_name,
                  char *dst, size_t dst_size) {
   const char *s, *p, *end;
   int name_len, len = -1;
   
   if (dst == NULL || dst_size == 0) {
      len = -2;
   } else if (var_name == NULL || (s = cookie_header) == NULL) {
      len = -1;
      dst[0] = '\0';
   } else {
      name_len = (int) strlen(var_name);
      end = s + strlen(s);
      dst[0] = '\0';
      
      for (; (s = mg_strcasestr(s, var_name)) != NULL; s += name_len) {
         if (s[name_len] == '=') {
            s += name_len + 1;
            if ((p = strchr(s, ' ')) == NULL)
               p = end;
            if (p[-1] == ';')
               p--;
            if (*s == '"' && p[-1] == '"' && p > s + 1) {
               s++;
               p--;
            }
            if ((size_t) (p - s) < dst_size) {
               len = p - s;
               mg_strlcpy(dst, s, (size_t) len + 1);
            } else {
               len = -3;
            }
            break;
         }
      }
   }
   return len;
}

static void convert_uri_to_file_name(struct mg_connection *conn, char *buf,
                                     size_t buf_len, struct file *filep) {
   struct vec a, b;
   const char *rewrite, *uri = conn->request_info.uri;
   char *p;
   int match_len;
   char gz_path[PATH_MAX];
   char const* accept_encoding;
   
   // Using buf_len - 1 because memmove() for PATH_INFO may shift part
   // of the path one byte on the right.
   mg_snprintf(conn, buf, buf_len - 1, "%s%s", conn->ctx->config[DOCUMENT_ROOT],
               uri);
   
   rewrite = conn->ctx->config[REWRITE];
   while ((rewrite = next_option(rewrite, &a, &b)) != NULL) {
      if ((match_len = match_prefix(a.ptr, a.len, uri)) > 0) {
         mg_snprintf(conn, buf, buf_len - 1, "%.*s%s", (int) b.len, b.ptr,
                     uri + match_len);
         break;
      }
   }
   
   if (mg_stat(conn, buf, filep)) return;
   
   // if we can't find the actual file, look for the file
   // with the same name but a .gz extension. If we find it,
   // use that and set the gzipped flag in the file struct
   // to indicate that the response need to have the content-
   // encoding: gzip header
   // we can only do this if the browser declares support
   if ((accept_encoding = mg_get_header(conn, "Accept-Encoding")) != NULL) {
      if (strstr(accept_encoding,"gzip") != NULL) {
         snprintf(gz_path, sizeof(gz_path), "%s.gz", buf);
         if (mg_stat(conn, gz_path, filep)) {
            filep->gzipped = 1;
            return;
         }
      }
   }
   
   // Support PATH_INFO for CGI scripts.
   for (p = buf + strlen(buf); p > buf + 1; p--) {
      if (*p == '/') {
         *p = '\0';
         if (match_prefix(conn->ctx->config[CGI_EXTENSIONS],
                          strlen(conn->ctx->config[CGI_EXTENSIONS]), buf) > 0 &&
             mg_stat(conn, buf, filep)) {
            // Shift PATH_INFO block one character right, e.g.
            //  "/x.cgi/foo/bar\x00" => "/x.cgi\x00/foo/bar\x00"
            // conn->path_info is pointing to the local variable "path" declared
            // in handle_request(), so PATH_INFO is not valid after
            // handle_request returns.
            conn->path_info = p + 1;
            memmove(p + 2, p + 1, strlen(p + 1) + 1);  // +1 is for trailing \0
            p[1] = '/';
            break;
         } else {
            *p = '/';
         }
      }
   }
}

// Check whether full request is buffered. Return:
//   -1  if request is malformed
//    0  if request is not yet fully buffered
//   >0  actual request length, including last \r\n\r\n
static int get_request_len(const char *buf, int buflen) {
   const char *s, *e;
   int len = 0;
   
   for (s = buf, e = s + buflen - 1; len <= 0 && s < e; s++)
      // Control characters are not allowed but >=128 is.
      if (!isprint(* (const unsigned char *) s) && *s != '\r' &&
          *s != '\n' && * (const unsigned char *) s < 128) {
         len = -1;
         break;  // [i_a] abort scan as soon as one malformed character is found;
         // don't let subsequent \r\n\r\n win us over anyhow
      } else if (s[0] == '\n' && s[1] == '\n') {
         len = (int) (s - buf) + 2;
      } else if (s[0] == '\n' && &s[1] < e &&
                 s[1] == '\r' && s[2] == '\n') {
         len = (int) (s - buf) + 3;
      }
   
   return len;
}

// Convert month to the month number. Return -1 on error, or month number
static int get_month_index(const char *s) {
   size_t i;
   
   for (i = 0; i < ARRAY_SIZE(month_names); i++)
      if (!strcmp(s, month_names[i]))
         return (int) i;
   
   return -1;
}

static int num_leap_years(int year) {
   return year / 4 - year / 100 + year / 400;
}

// Parse UTC date-time string, and return the corresponding time_t value.
static time_t parse_date_string(const char *datetime) {
   static const unsigned short days_before_month[] = {
      0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
   };
   char month_str[32];
   int second, minute, hour, day, month, year, leap_days, days;
   time_t result = (time_t) 0;
   
   if (((sscanf(datetime, "%d/%3s/%d %d:%d:%d",
                &day, month_str, &year, &hour, &minute, &second) == 6) ||
        (sscanf(datetime, "%d %3s %d %d:%d:%d",
                &day, month_str, &year, &hour, &minute, &second) == 6) ||
        (sscanf(datetime, "%*3s, %d %3s %d %d:%d:%d",
                &day, month_str, &year, &hour, &minute, &second) == 6) ||
        (sscanf(datetime, "%d-%3s-%d %d:%d:%d",
                &day, month_str, &year, &hour, &minute, &second) == 6)) &&
       year > 1970 &&
       (month = get_month_index(month_str)) != -1) {
      leap_days = num_leap_years(year) - num_leap_years(1970);
      year -= 1970;
      days = year * 365 + days_before_month[month] + (day - 1) + leap_days;
      result = days * 24 * 3600 + hour * 3600 + minute * 60 + second;
   }
   
   return result;
}

// Protect against directory disclosure attack by removing '..',
// excessive '/' and '\' characters
static void remove_double_dots_and_double_slashes(char *s) {
   char *p = s;
   
   while (*s != '\0') {
      *p++ = *s++;
      if (s[-1] == '/' || s[-1] == '\\') {
         // Skip all following slashes, backslashes and double-dots
         while (s[0] != '\0') {
            if (s[0] == '/' || s[0] == '\\') {
               s++;
            } else if (s[0] == '.' && s[1] == '.') {
               s += 2;
            } else {
               break;
            }
         }
      }
   }
   *p = '\0';
}

static const struct {
   const char *extension;
   size_t ext_len;
   const char *mime_type;
} builtin_mime_types[] = {
   {".html", 5, "text/html"},
   {".htm", 4, "text/html"},
   {".shtm", 5, "text/html"},
   {".shtml", 6, "text/html"},
   {".css", 4, "text/css"},
   {".js",  3, "application/x-javascript"},
   {".ico", 4, "image/x-icon"},
   {".gif", 4, "image/gif"},
   {".jpg", 4, "image/jpeg"},
   {".jpeg", 5, "image/jpeg"},
   {".png", 4, "image/png"},
   {".svg", 4, "image/svg+xml"},
   {".txt", 4, "text/plain"},
   {".torrent", 8, "application/x-bittorrent"},
   {".wav", 4, "audio/x-wav"},
   {".mp3", 4, "audio/x-mp3"},
   {".mid", 4, "audio/mid"},
   {".m3u", 4, "audio/x-mpegurl"},
   {".ogg", 4, "audio/ogg"},
   {".ram", 4, "audio/x-pn-realaudio"},
   {".xml", 4, "text/xml"},
   {".json",  5, "text/json"},
   {".xslt", 5, "application/xml"},
   {".xsl", 4, "application/xml"},
   {".ra",  3, "audio/x-pn-realaudio"},
   {".doc", 4, "application/msword"},
   {".exe", 4, "application/octet-stream"},
   {".zip", 4, "application/x-zip-compressed"},
   {".xls", 4, "application/excel"},
   {".tgz", 4, "application/x-tar-gz"},
   {".tar", 4, "application/x-tar"},
   {".gz",  3, "application/x-gunzip"},
   {".arj", 4, "application/x-arj-compressed"},
   {".rar", 4, "application/x-arj-compressed"},
   {".rtf", 4, "application/rtf"},
   {".pdf", 4, "application/pdf"},
   {".swf", 4, "application/x-shockwave-flash"},
   {".mpg", 4, "video/mpeg"},
   {".webm", 5, "video/webm"},
   {".mpeg", 5, "video/mpeg"},
   {".mov", 4, "video/quicktime"},
   {".mp4", 4, "video/mp4"},
   {".m4v", 4, "video/x-m4v"},
   {".asf", 4, "video/x-ms-asf"},
   {".avi", 4, "video/x-msvideo"},
   {".bmp", 4, "image/bmp"},
   {".ttf", 4, "application/x-font-ttf"},
   {NULL,  0, NULL}
};

const char *mg_get_builtin_mime_type(const char *path) {
   const char *ext;
   size_t i, path_len;
   
   path_len = strlen(path);
   
   for (i = 0; builtin_mime_types[i].extension != NULL; i++) {
      ext = path + (path_len - builtin_mime_types[i].ext_len);
      if (path_len > builtin_mime_types[i].ext_len &&
          mg_strcasecmp(ext, builtin_mime_types[i].extension) == 0) {
         return builtin_mime_types[i].mime_type;
      }
   }
   
   return "text/plain";
}

// Look at the "path" extension and figure what mime type it has.
// Store mime type in the vector.
static void get_mime_type(struct mg_context *ctx, const char *path,
                          struct vec *vec) {
   struct vec ext_vec, mime_vec;
   const char *list, *ext;
   size_t path_len;
   
   path_len = strlen(path);
   
   // Scan user-defined mime types first, in case user wants to
   // override default mime types.
   list = ctx->config[EXTRA_MIME_TYPES];
   while ((list = next_option(list, &ext_vec, &mime_vec)) != NULL) {
      // ext now points to the path suffix
      ext = path + path_len - ext_vec.len;
      if (mg_strncasecmp(ext, ext_vec.ptr, ext_vec.len) == 0) {
         *vec = mime_vec;
         return;
      }
   }
   
   vec->ptr = mg_get_builtin_mime_type(path);
   vec->len = strlen(vec->ptr);
}

static int is_big_endian(void) {
   static const int n = 1;
   return ((char *) &n)[0] == 0;
}

#ifndef HAVE_MD5
typedef struct MD5Context {
   uint32_t buf[4];
   uint32_t bits[2];
   unsigned char in[64];
} MD5_CTX;

static void byteReverse(unsigned char *buf, unsigned longs) {
   uint32_t t;
   
   // Forrest: MD5 expect LITTLE_ENDIAN, swap if BIG_ENDIAN
   if (is_big_endian()) {
      do {
         t = (uint32_t) ((unsigned) buf[3] << 8 | buf[2]) << 16 |
         ((unsigned) buf[1] << 8 | buf[0]);
         * (uint32_t *) buf = t;
         buf += 4;
      } while (--longs);
   }
}

#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))

#define MD5STEP(f, w, x, y, z, data, s) \
( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )

// Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
// initialization constants.
static void MD5Init(MD5_CTX *ctx) {
   ctx->buf[0] = 0x67452301;
   ctx->buf[1] = 0xefcdab89;
   ctx->buf[2] = 0x98badcfe;
   ctx->buf[3] = 0x10325476;
   
   ctx->bits[0] = 0;
   ctx->bits[1] = 0;
}

static void MD5Transform(uint32_t buf[4], uint32_t const in[16]) {
   register uint32_t a, b, c, d;
   
   a = buf[0];
   b = buf[1];
   c = buf[2];
   d = buf[3];
   
   MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
   MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
   MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
   MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
   MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
   MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
   MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
   MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
   MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
   MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
   MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
   MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
   MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
   MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
   MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
   MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);
   
   MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
   MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
   MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
   MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
   MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
   MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
   MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
   MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
   MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
   MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
   MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
   MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
   MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
   MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
   MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
   MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);
   
   MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
   MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
   MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
   MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
   MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
   MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
   MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
   MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
   MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
   MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
   MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
   MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
   MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
   MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
   MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
   MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);
   
   MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
   MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
   MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
   MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
   MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
   MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
   MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
   MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
   MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
   MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
   MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
   MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
   MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
   MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
   MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
   MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);
   
   buf[0] += a;
   buf[1] += b;
   buf[2] += c;
   buf[3] += d;
}

static void MD5Update(MD5_CTX *ctx, unsigned char const *buf, unsigned len) {
   uint32_t t;
   
   t = ctx->bits[0];
   if ((ctx->bits[0] = t + ((uint32_t) len << 3)) < t)
      ctx->bits[1]++;
   ctx->bits[1] += len >> 29;
   
   t = (t >> 3) & 0x3f;
   
   if (t) {
      unsigned char *p = (unsigned char *) ctx->in + t;
      
      t = 64 - t;
      if (len < t) {
         memcpy(p, buf, len);
         return;
      }
      memcpy(p, buf, t);
      byteReverse(ctx->in, 16);
      MD5Transform(ctx->buf, (uint32_t *) ctx->in);
      buf += t;
      len -= t;
   }
   
   while (len >= 64) {
      memcpy(ctx->in, buf, 64);
      byteReverse(ctx->in, 16);
      MD5Transform(ctx->buf, (uint32_t *) ctx->in);
      buf += 64;
      len -= 64;
   }
   
   memcpy(ctx->in, buf, len);
}

static void MD5Final(unsigned char digest[16], MD5_CTX *ctx) {
   unsigned count;
   unsigned char *p;
   uint32_t *a;
   
   count = (ctx->bits[0] >> 3) & 0x3F;
   
   p = ctx->in + count;
   *p++ = 0x80;
   count = 64 - 1 - count;
   if (count < 8) {
      memset(p, 0, count);
      byteReverse(ctx->in, 16);
      MD5Transform(ctx->buf, (uint32_t *) ctx->in);
      memset(ctx->in, 0, 56);
   } else {
      memset(p, 0, count - 8);
   }
   byteReverse(ctx->in, 14);
   
   a = (uint32_t *)ctx->in;
   a[14] = ctx->bits[0];
   a[15] = ctx->bits[1];
   
   MD5Transform(ctx->buf, (uint32_t *) ctx->in);
   byteReverse((unsigned char *) ctx->buf, 4);
   memcpy(digest, ctx->buf, 16);
   memset((char *) ctx, 0, sizeof(*ctx));
}
#endif // !HAVE_MD5

// Stringify binary data. Output buffer must be twice as big as input,
// because each byte takes 2 bytes in string representation
static void bin2str(char *to, const unsigned char *p, size_t len) {
   static const char *hex = "0123456789abcdef";
   
   for (; len--; p++) {
      *to++ = hex[p[0] >> 4];
      *to++ = hex[p[0] & 0x0f];
   }
   *to = '\0';
}

// Return stringified MD5 hash for list of strings. Buffer must be 33 bytes.
char *mg_md5(char buf[33], ...) {
   unsigned char hash[16];
   const char *p;
   va_list ap;
   MD5_CTX ctx;
   
   MD5Init(&ctx);
   
   va_start(ap, buf);
   while ((p = va_arg(ap, const char *)) != NULL) {
      MD5Update(&ctx, (const unsigned char *) p, (unsigned) strlen(p));
   }
   va_end(ap);
   
   MD5Final(hash, &ctx);
   bin2str(buf, hash, sizeof(hash));
   return buf;
}

// Check the user's password, return 1 if OK
static int check_password(const char *method, const char *ha1, const char *uri,
                          const char *nonce, const char *nc, const char *cnonce,
                          const char *qop, const char *response) {
   char ha2[32 + 1], expected_response[32 + 1];
   
   // Some of the parameters may be NULL
   if (method == NULL || nonce == NULL || nc == NULL || cnonce == NULL ||
       qop == NULL || response == NULL) {
      return 0;
   }
   
   // NOTE(lsm): due to a bug in MSIE, we do not compare the URI
   // TODO(lsm): check for authentication timeout
   if (// strcmp(dig->uri, c->ouri) != 0 ||
       strlen(response) != 32
       // || now - strtoul(dig->nonce, NULL, 10) > 3600
       ) {
      return 0;
   }
   
   mg_md5(ha2, method, ":", uri, NULL);
   mg_md5(expected_response, ha1, ":", nonce, ":", nc,
          ":", cnonce, ":", qop, ":", ha2, NULL);
   
   return mg_strcasecmp(response, expected_response) == 0;
}

// Use the global passwords file, if specified by auth_gpass option,
// or search for .htpasswd in the requested directory.
static void open_auth_file(struct mg_connection *conn, const char *path,
                           struct file *filep) {
   char name[PATH_MAX];
   const char *p, *e, *gpass = conn->ctx->config[GLOBAL_PASSWORDS_FILE];
   struct file file = STRUCT_FILE_INITIALIZER;
   
   if (gpass != NULL) {
      // Use global passwords file
      if (!mg_fopen(conn, gpass, "r", filep)) {
         cry(conn, "fopen(%s): %s", gpass, strerror(ERRNO));
      }
      // Important: using local struct file to test path for is_directory flag.
      // If filep is used, mg_stat() makes it appear as if auth file was opened.
   } else if (mg_stat(conn, path, &file) && file.is_directory) {
      mg_snprintf(conn, name, sizeof(name), "%s%c%s",
                  path, '/', PASSWORDS_FILE_NAME);
      mg_fopen(conn, name, "r", filep);
   } else {
      // Try to find .htpasswd in requested directory.
      for (p = path, e = p + strlen(p) - 1; e > p; e--)
         if (e[0] == '/')
            break;
      mg_snprintf(conn, name, sizeof(name), "%.*s%c%s",
                  (int) (e - p), p, '/', PASSWORDS_FILE_NAME);
      mg_fopen(conn, name, "r", filep);
   }
}

// Parsed Authorization header
struct ah {
   char *user, *uri, *cnonce, *response, *qop, *nc, *nonce;
};

// Return 1 on success. Always initializes the ah structure.
static int parse_auth_header(struct mg_connection *conn, char *buf,
                             size_t buf_size, struct ah *ah) {
   char *name, *value, *s;
   const char *auth_header;
   
   (void) memset(ah, 0, sizeof(*ah));
   if ((auth_header = mg_get_header(conn, "Authorization")) == NULL ||
       mg_strncasecmp(auth_header, "Digest ", 7) != 0) {
      return 0;
   }
   
   // Make modifiable copy of the auth header
   (void) mg_strlcpy(buf, auth_header + 7, buf_size);
   s = buf;
   
   // Parse authorization header
   for (;;) {
      // Gobble initial spaces
      while (isspace(* (unsigned char *) s)) {
         s++;
      }
      name = skip_quoted(&s, "=", " ", 0);
      // Value is either quote-delimited, or ends at first comma or space.
      if (s[0] == '\"') {
         s++;
         value = skip_quoted(&s, "\"", " ", '\\');
         if (s[0] == ',') {
            s++;
         }
      } else {
         value = skip_quoted(&s, ", ", " ", 0);  // IE uses commas, FF uses spaces
      }
      if (*name == '\0') {
         break;
      }
      
      if (!strcmp(name, "username")) {
         ah->user = value;
      } else if (!strcmp(name, "cnonce")) {
         ah->cnonce = value;
      } else if (!strcmp(name, "response")) {
         ah->response = value;
      } else if (!strcmp(name, "uri")) {
         ah->uri = value;
      } else if (!strcmp(name, "qop")) {
         ah->qop = value;
      } else if (!strcmp(name, "nc")) {
         ah->nc = value;
      } else if (!strcmp(name, "nonce")) {
         ah->nonce = value;
      }
   }
   
   // CGI needs it as REMOTE_USER
   if (ah->user != NULL) {
      conn->request_info.remote_user = mg_strdup(ah->user);
   } else {
      return 0;
   }
   
   return 1;
}

static char *mg_fgets(char *buf, size_t size, struct file *filep, char **p) {
   char *eof;
   size_t len;
   
   if (filep->membuf != NULL && *p != NULL) {
      eof = memchr(*p, '\n', &filep->membuf[filep->size] - *p);
      len = (size_t) (eof - *p) > size - 1 ? size - 1 : (size_t) (eof - *p);
      memcpy(buf, *p, len);
      buf[len] = '\0';
      *p = eof;
      return eof;
   } else if (filep->fp != NULL) {
      return fgets(buf, size, filep->fp);
   } else {
      return NULL;
   }
}

// Authorize against the opened passwords file. Return 1 if authorized.
static int authorize(struct mg_connection *conn, struct file *filep) {
   struct ah ah;
   char line[256], f_user[256], ha1[256], f_domain[256], buf[MG_BUF_LEN], *p;
   
   if (!parse_auth_header(conn, buf, sizeof(buf), &ah)) {
      return 0;
   }
   
   // Loop over passwords file
   p = (char *) filep->membuf;
   while (mg_fgets(line, sizeof(line), filep, &p) != NULL) {
      if (sscanf(line, "%[^:]:%[^:]:%s", f_user, f_domain, ha1) != 3) {
         continue;
      }
      
      if (!strcmp(ah.user, f_user) &&
          !strcmp(conn->ctx->config[AUTHENTICATION_DOMAIN], f_domain))
         return check_password(conn->request_info.request_method, ha1, ah.uri,
                               ah.nonce, ah.nc, ah.cnonce, ah.qop, ah.response);
   }
   
   return 0;
}

// Return 1 if request is authorised, 0 otherwise.
static int check_authorization(struct mg_connection *conn, const char *path) {
   char fname[PATH_MAX];
   struct vec uri_vec, filename_vec;
   const char *list;
   struct file file = STRUCT_FILE_INITIALIZER;
   int authorized = 1;
   
   list = conn->ctx->config[PROTECT_URI];
   while ((list = next_option(list, &uri_vec, &filename_vec)) != NULL) {
      if (!memcmp(conn->request_info.uri, uri_vec.ptr, uri_vec.len)) {
         mg_snprintf(conn, fname, sizeof(fname), "%.*s",
                     (int) filename_vec.len, filename_vec.ptr);
         if (!mg_fopen(conn, fname, "r", &file)) {
            cry(conn, "%s: cannot open %s: %s", __func__, fname, strerror(errno));
         }
         break;
      }
   }
   
   if (!is_file_opened(&file)) {
      open_auth_file(conn, path, &file);
   }
   
   if (is_file_opened(&file)) {
      authorized = authorize(conn, &file);
      mg_fclose(&file);
   }
   
   return authorized;
}

static void send_authorization_request(struct mg_connection *conn) {
   conn->status_code = 401;
   mg_printf(conn,
             "HTTP/1.1 401 Unauthorized\r\n"
             "Content-Length: 0\r\n"
             "WWW-Authenticate: Digest qop=\"auth\", "
             "realm=\"%s\", nonce=\"%lu\"\r\n\r\n",
             conn->ctx->config[AUTHENTICATION_DOMAIN],
             (unsigned long) time(NULL));
}

static int is_authorized_for_put(struct mg_connection *conn) {
   struct file file = STRUCT_FILE_INITIALIZER;
   const char *passfile = conn->ctx->config[PUT_DELETE_PASSWORDS_FILE];
   int ret = 0;
   
   if (passfile != NULL && mg_fopen(conn, passfile, "r", &file)) {
      ret = authorize(conn, &file);
      mg_fclose(&file);
   }
   
   return ret;
}

int mg_modify_passwords_file(const char *fname, const char *domain,
                             const char *user, const char *pass) {
   int found;
   char line[512], u[512], d[512], ha1[33], tmp[PATH_MAX];
   FILE *fp, *fp2;
   
   found = 0;
   fp = fp2 = NULL;
   
   // Regard empty password as no password - remove user record.
   if (pass != NULL && pass[0] == '\0') {
      pass = NULL;
   }
   
   (void) snprintf(tmp, sizeof(tmp), "%s.tmp", fname);
   
   // Create the file if does not exist
   if ((fp = fopen(fname, "a+")) != NULL) {
      (void) fclose(fp);
   }
   
   // Open the given file and temporary file
   if ((fp = fopen(fname, "r")) == NULL) {
      return 0;
   } else if ((fp2 = fopen(tmp, "w+")) == NULL) {
      fclose(fp);
      return 0;
   }
   
   // Copy the stuff to temporary file
   while (fgets(line, sizeof(line), fp) != NULL) {
      if (sscanf(line, "%[^:]:%[^:]:%*s", u, d) != 2) {
         continue;
      }
      
      if (!strcmp(u, user) && !strcmp(d, domain)) {
         found++;
         if (pass != NULL) {
            mg_md5(ha1, user, ":", domain, ":", pass, NULL);
            fprintf(fp2, "%s:%s:%s\n", user, domain, ha1);
         }
      } else {
         fprintf(fp2, "%s", line);
      }
   }
   
   // If new user, just add it
   if (!found && pass != NULL) {
      mg_md5(ha1, user, ":", domain, ":", pass, NULL);
      fprintf(fp2, "%s:%s:%s\n", user, domain, ha1);
   }
   
   // Close files
   fclose(fp);
   fclose(fp2);
   
   // Put the temp file in place of real file
   remove(fname);
   rename(tmp, fname);
   
   return 1;
}

static int conn2(const char *host, int port, int use_ssl,
                 char *ebuf, size_t ebuf_len) {
   struct sockaddr_in sin;
   struct hostent *he;
   SOCKET sock = INVALID_SOCKET;
   
   if (host == NULL) {
      snprintf(ebuf, ebuf_len, "%s", "NULL host");
   } else if (use_ssl && SSLv23_client_method == NULL) {
      snprintf(ebuf, ebuf_len, "%s", "SSL is not initialized");
      // TODO(lsm): use something threadsafe instead of gethostbyname()
   } else if ((he = gethostbyname(host)) == NULL) {
      snprintf(ebuf, ebuf_len, "gethostbyname(%s): %s", host, strerror(ERRNO));
   } else if ((sock = socket(PF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) {
      snprintf(ebuf, ebuf_len, "socket(): %s", strerror(ERRNO));
   } else {
      sin.sin_family = AF_INET;
      sin.sin_port = htons((uint16_t) port);
      sin.sin_addr = * (struct in_addr *) he->h_addr_list[0];
      if (connect(sock, (struct sockaddr *) &sin, sizeof(sin)) != 0) {
         snprintf(ebuf, ebuf_len, "connect(%s:%d): %s",
                  host, port, strerror(ERRNO));
         closesocket(sock);
         sock = INVALID_SOCKET;
      }
   }
   return sock;
}



void mg_url_encode(const char *src, char *dst, size_t dst_len) {
   static const char *dont_escape = "._-$,;~()";
   static const char *hex = "0123456789abcdef";
   const char *end = dst + dst_len - 1;
   
   for (; *src != '\0' && dst < end; src++, dst++) {
      if (isalnum(*(const unsigned char *) src) ||
          strchr(dont_escape, * (const unsigned char *) src) != NULL) {
         *dst = *src;
      } else if (dst + 2 < end) {
         dst[0] = '%';
         dst[1] = hex[(* (const unsigned char *) src) >> 4];
         dst[2] = hex[(* (const unsigned char *) src) & 0xf];
         dst += 2;
      }
   }
   
   *dst = '\0';
}

static void print_dir_entry(struct de *de) {
   char size[64], mod[64], href[PATH_MAX];
   
   if (de->file.is_directory) {
      mg_snprintf(de->conn, size, sizeof(size), "%s", "[DIRECTORY]");
   } else {
      // We use (signed) cast below because MSVC 6 compiler cannot
      // convert unsigned __int64 to double. Sigh.
      if (de->file.size < 1024) {
         mg_snprintf(de->conn, size, sizeof(size), "%d", (int) de->file.size);
      } else if (de->file.size < 0x100000) {
         mg_snprintf(de->conn, size, sizeof(size),
                     "%.1fk", (double) de->file.size / 1024.0);
      } else if (de->file.size < 0x40000000) {
         mg_snprintf(de->conn, size, sizeof(size),
                     "%.1fM", (double) de->file.size / 1048576);
      } else {
         mg_snprintf(de->conn, size, sizeof(size),
                     "%.1fG", (double) de->file.size / 1073741824);
      }
   }
   strftime(mod, sizeof(mod), "%d-%b-%Y %H:%M",
            localtime(&de->file.modification_time));
   mg_url_encode(de->file_name, href, sizeof(href));
   de->conn->num_bytes_sent += mg_printf(de->conn,
                                         "<tr><td><a href=\"%s%s%s\">%s%s</a></td>"
                                         "<td>&nbsp;%s</td><td>&nbsp;&nbsp;%s</td></tr>\n",
                                         de->conn->request_info.uri, href, de->file.is_directory ? "/" : "",
                                         de->file_name, de->file.is_directory ? "/" : "", mod, size);
}

// This function is called from send_directory() and used for
// sorting directory entries by size, or name, or modification time.
// On windows, __cdecl specification is needed in case if project is built
// with __stdcall convention. qsort always requires __cdels callback.
static int WINCDECL compare_dir_entries(const void *p1, const void *p2) {
   const struct de *a = (const struct de *) p1, *b = (const struct de *) p2;
   const char *query_string = a->conn->request_info.query_string;
   int cmp_result = 0;
   
   if (query_string == NULL) {
      query_string = "na";
   }
   
   if (a->file.is_directory && !b->file.is_directory) {
      return -1;  // Always put directories on top
   } else if (!a->file.is_directory && b->file.is_directory) {
      return 1;   // Always put directories on top
   } else if (*query_string == 'n') {
      cmp_result = strcmp(a->file_name, b->file_name);
   } else if (*query_string == 's') {
      cmp_result = a->file.size == b->file.size ? 0 :
      a->file.size > b->file.size ? 1 : -1;
   } else if (*query_string == 'd') {
      cmp_result = a->file.modification_time == b->file.modification_time ? 0 :
      a->file.modification_time > b->file.modification_time ? 1 : -1;
   }
   
   return query_string[1] == 'd' ? -cmp_result : cmp_result;
}

static int must_hide_file(struct mg_connection *conn, const char *path) {
   const char *pw_pattern = "**" PASSWORDS_FILE_NAME "$";
   const char *pattern = conn->ctx->config[HIDE_FILES];
   return match_prefix(pw_pattern, strlen(pw_pattern), path) > 0 ||
   (pattern != NULL && match_prefix(pattern, strlen(pattern), path) > 0);
}

static int scan_directory(struct mg_connection *conn, const char *dir,
                          void *data, void (*cb)(struct de *, void *)) {
   char path[PATH_MAX];
   struct dirent *dp;
   DIR *dirp;
   struct de de;
   
   if ((dirp = opendir(dir)) == NULL) {
      return 0;
   } else {
      de.conn = conn;
      
      while ((dp = readdir(dirp)) != NULL) {
         // Do not show current dir and hidden files
         if (!strcmp(dp->d_name, ".") ||
             !strcmp(dp->d_name, "..") ||
             must_hide_file(conn, dp->d_name)) {
            continue;
         }
         
         mg_snprintf(conn, path, sizeof(path), "%s%c%s", dir, '/', dp->d_name);
         
         // If we don't memset stat structure to zero, mtime will have
         // garbage and strftime() will segfault later on in
         // print_dir_entry(). memset is required only if mg_stat()
         // fails. For more details, see
         // http://code.google.com/p/mongoose/issues/detail?id=79
         memset(&de.file, 0, sizeof(de.file));
         mg_stat(conn, path, &de.file);
         
         de.file_name = dp->d_name;
         cb(&de, data);
      }
      (void) closedir(dirp);
   }
   return 1;
}

struct dir_scan_data {
   struct de *entries;
   int num_entries;
   int arr_size;
};

// Behaves like realloc(), but frees original pointer on failure
static void *realloc2(void *ptr, size_t size) {
   void *new_ptr = realloc(ptr, size);
   if (new_ptr == NULL) {
      free(ptr);
   }
   return new_ptr;
}

static void dir_scan_callback(struct de *de, void *data) {
   struct dir_scan_data *dsd = (struct dir_scan_data *) data;
   
   if (dsd->entries == NULL || dsd->num_entries >= dsd->arr_size) {
      dsd->arr_size *= 2;
      dsd->entries = (struct de *) realloc2(dsd->entries, dsd->arr_size *
                                            sizeof(dsd->entries[0]));
   }
   if (dsd->entries == NULL) {
      // TODO(lsm): propagate an error to the caller
      dsd->num_entries = 0;
   } else {
      dsd->entries[dsd->num_entries].file_name = mg_strdup(de->file_name);
      dsd->entries[dsd->num_entries].file = de->file;
      dsd->entries[dsd->num_entries].conn = de->conn;
      dsd->num_entries++;
   }
}

static void handle_directory_request(struct mg_connection *conn,
                                     const char *dir) {
   int i, sort_direction;
   struct dir_scan_data data = { NULL, 0, 128 };
   
   if (!scan_directory(conn, dir, &data, dir_scan_callback)) {
      send_http_error(conn, 500, "Cannot open directory",
                      "Error: opendir(%s): %s", dir, strerror(ERRNO));
      return;
   }
   
   sort_direction = conn->request_info.query_string != NULL &&
   conn->request_info.query_string[1] == 'd' ? 'a' : 'd';
   
   conn->must_close = 1;
   mg_printf(conn, "%s",
             "HTTP/1.1 200 OK\r\n"
             "Connection: close\r\n"
             "Content-Type: text/html; charset=utf-8\r\n\r\n");
   
   conn->num_bytes_sent += mg_printf(conn,
                                     "<html><head><title>Index of %s</title>"
                                     "<style>th {text-align: left;}</style></head>"
                                     "<body><h1>Index of %s</h1><pre><table cellpadding=\"0\">"
                                     "<tr><th><a href=\"?n%c\">Name</a></th>"
                                     "<th><a href=\"?d%c\">Modified</a></th>"
                                     "<th><a href=\"?s%c\">Size</a></th></tr>"
                                     "<tr><td colspan=\"3\"><hr></td></tr>",
                                     conn->request_info.uri, conn->request_info.uri,
                                     sort_direction, sort_direction, sort_direction);
   
   // Print first entry - link to a parent directory
   conn->num_bytes_sent += mg_printf(conn,
                                     "<tr><td><a href=\"%s%s\">%s</a></td>"
                                     "<td>&nbsp;%s</td><td>&nbsp;&nbsp;%s</td></tr>\n",
                                     conn->request_info.uri, "..", "Parent directory", "-", "-");
   
   // Sort and print directory entries
   qsort(data.entries, (size_t) data.num_entries, sizeof(data.entries[0]),
         compare_dir_entries);
   for (i = 0; i < data.num_entries; i++) {
      print_dir_entry(&data.entries[i]);
      free(data.entries[i].file_name);
   }
   free(data.entries);
   
   conn->num_bytes_sent += mg_printf(conn, "%s", "</table></body></html>");
   conn->status_code = 200;
}

// Send len bytes from the opened file to the client.
static void send_file_data(struct mg_connection *conn, struct file *filep,
                           int64_t offset, int64_t len) {
   char buf[MG_BUF_LEN];
   int to_read, num_read, num_written;
   
   // Sanity check the offset
   offset = offset < 0 ? 0 : offset > filep->size ? filep->size : offset;
   
   if (len > 0 && filep->membuf != NULL && filep->size > 0) {
      if (len > filep->size - offset) {
         len = filep->size - offset;
      }
      mg_write(conn, filep->membuf + offset, (size_t) len);
   } else if (len > 0 && filep->fp != NULL) {
      fseeko(filep->fp, offset, SEEK_SET);
      while (len > 0) {
         // Calculate how much to read from the file in the buffer
         to_read = sizeof(buf);
         if ((int64_t) to_read > len) {
            to_read = (int) len;
         }
         
         // Read from file, exit the loop on error
         if ((num_read = fread(buf, 1, (size_t) to_read, filep->fp)) <= 0) {
            break;
         }
         
         // Send read bytes to the client, exit the loop on error
         if ((num_written = mg_write(conn, buf, (size_t) num_read)) != num_read) {
            break;
         }
         
         // Both read and were successful, adjust counters
         conn->num_bytes_sent += num_written;
         len -= num_written;
      }
   }
}

static int parse_range_header(const char *header, int64_t *a, int64_t *b) {
   return sscanf(header, "bytes=%" INT64_FMT "-%" INT64_FMT, a, b);
}

static void gmt_time_string(char *buf, size_t buf_len, time_t *t) {
   strftime(buf, buf_len, "%a, %d %b %Y %H:%M:%S GMT", gmtime(t));
}

static void construct_etag(char *buf, size_t buf_len,
                           const struct file *filep) {
   snprintf(buf, buf_len, "\"%lx.%" INT64_FMT "\"",
            (unsigned long) filep->modification_time, filep->size);
}

static void fclose_on_exec(struct file *filep) {
   if (filep != NULL && filep->fp != NULL) {
#ifndef _WIN32
      fcntl(fileno(filep->fp), F_SETFD, FD_CLOEXEC);
#endif
   }
}

static void handle_file_request(struct mg_connection *conn, const char *path,
                                struct file *filep) {
   char date[64], lm[64], etag[64], range[64];
   const char *msg = "OK", *hdr;
   time_t curtime = time(NULL);
   int64_t cl, r1, r2;
   struct vec mime_vec;
   int n;
   char gz_path[PATH_MAX];
   char const* encoding = "";
   
   get_mime_type(conn->ctx, path, &mime_vec);
   cl = filep->size;
   conn->status_code = 200;
   range[0] = '\0';
   
   // if this file is in fact a pre-gzipped file, rewrite its filename
   // it's important to rewrite the filename after resolving
   // the mime type from it, to preserve the actual file's type
   if (filep->gzipped) {
      snprintf(gz_path, sizeof(gz_path), "%s.gz", path);
      path = gz_path;
      encoding = "Content-Encoding: gzip\r\n";
   }
   
   if (!mg_fopen(conn, path, "rb", filep)) {
      send_http_error(conn, 500, http_500_error,
                      "fopen(%s): %s", path, strerror(ERRNO));
      return;
   }
   
   fclose_on_exec(filep);
   
   // If Range: header specified, act accordingly
   r1 = r2 = 0;
   hdr = mg_get_header(conn, "Range");
   if (hdr != NULL && (n = parse_range_header(hdr, &r1, &r2)) > 0 &&
       r1 >= 0 && r2 >= 0) {
      // actually, range requests don't play well with a pre-gzipped
      // file (since the range is specified in the uncmpressed space)
      if (filep->gzipped) {
         send_http_error(conn, 501, "Not Implemented", "range requests in gzipped files are not supported");
         return;
      }
      conn->status_code = 206;
      cl = n == 2 ? (r2 > cl ? cl : r2) - r1 + 1: cl - r1;
      mg_snprintf(conn, range, sizeof(range),
                  "Content-Range: bytes "
                  "%" INT64_FMT "-%"
                  INT64_FMT "/%" INT64_FMT "\r\n",
                  r1, r1 + cl - 1, filep->size);
      msg = "Partial Content";
   }
   
   // Prepare Etag, Date, Last-Modified headers. Must be in UTC, according to
   // http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3
   gmt_time_string(date, sizeof(date), &curtime);
   gmt_time_string(lm, sizeof(lm), &filep->modification_time);
   construct_etag(etag, sizeof(etag), filep);
   
   (void) mg_printf(conn,
                    "HTTP/1.1 %d %s\r\n"
                    "Date: %s\r\n"
                    "Last-Modified: %s\r\n"
                    "Etag: %s\r\n"
                    "Content-Type: %.*s\r\n"
                    "Content-Length: %" INT64_FMT "\r\n"
                    "Connection: %s\r\n"
                    "Accept-Ranges: bytes\r\n"
                    "%s%s\r\n",
                    conn->status_code, msg, date, lm, etag, (int) mime_vec.len,
                    mime_vec.ptr, cl, suggest_connection_header(conn), range, encoding);
   
   if (strcmp(conn->request_info.request_method, "HEAD") != 0) {
      send_file_data(conn, filep, r1, cl);
   }
   mg_fclose(filep);
}

void mg_send_file(struct mg_connection *conn, const char *path) {
   struct file file = STRUCT_FILE_INITIALIZER;
   if (mg_stat(conn, path, &file)) {
      handle_file_request(conn, path, &file);
   } else {
      send_http_error(conn, 404, "Not Found", "%s", "File not found");
   }
}


// Parse HTTP headers from the given buffer, advance buffer to the point
// where parsing stopped.
static void parse_http_headers(char **buf, struct mg_request_info *ri) {
   int i;
   
   for (i = 0; i < (int) ARRAY_SIZE(ri->http_headers); i++) {
      ri->http_headers[i].name = skip_quoted(buf, ":", " ", 0);
      ri->http_headers[i].value = skip(buf, "\r\n");
      if (ri->http_headers[i].name[0] == '\0')
         break;
      ri->num_headers = i + 1;
   }
}

static int is_valid_http_method(const char *method) {
   return !strcmp(method, "GET") || !strcmp(method, "POST") ||
   !strcmp(method, "HEAD") || !strcmp(method, "CONNECT") ||
   !strcmp(method, "PUT") || !strcmp(method, "DELETE") ||
   !strcmp(method, "OPTIONS") || !strcmp(method, "PROPFIND");
}

// Parse HTTP request, fill in mg_request_info structure.
// This function modifies the buffer by NUL-terminating
// HTTP request components, header names and header values.
static int parse_http_message(char *buf, int len, struct mg_request_info *ri) {
   int is_request, request_length = get_request_len(buf, len);
   if (request_length > 0) {
      // Reset attributes. DO NOT TOUCH is_ssl, remote_ip, remote_port
      ri->remote_user = ri->request_method = ri->uri = ri->http_version = NULL;
      ri->num_headers = 0;
      
      buf[request_length - 1] = '\0';
      
      // RFC says that all initial whitespaces should be ingored
      while (*buf != '\0' && isspace(* (unsigned char *) buf)) {
         buf++;
      }
      ri->request_method = skip(&buf, " ");
      ri->uri = skip(&buf, " ");
      ri->http_version = skip(&buf, "\r\n");
      if (((is_request = is_valid_http_method(ri->request_method)) &&
           memcmp(ri->http_version, "HTTP/", 5) != 0) ||
          (!is_request && memcmp(ri->request_method, "HTTP/", 5)) != 0) {
         request_length = -1;
      } else {
         if (is_request) {
            ri->http_version += 5;
         }
         parse_http_headers(&buf, ri);
      }
   }
   return request_length;
}

// Keep reading the input (either opened file descriptor fd, or socket sock,
// or SSL descriptor ssl) into buffer buf, until \r\n\r\n appears in the
// buffer (which marks the end of HTTP request). Buffer buf may already
// have some data. The length of the data is stored in nread.
// Upon every read operation, increase nread by the number of bytes read.
static int read_request(FILE *fp, struct mg_connection *conn,
                        char *buf, int bufsiz, int *nread) {
   int request_len, n = 0;
   
   request_len = get_request_len(buf, *nread);
   while (*nread < bufsiz && request_len == 0 &&
          (n = pull(fp, conn, buf + *nread, bufsiz - *nread)) > 0) {
      *nread += n;
      assert(*nread <= bufsiz);
      request_len = get_request_len(buf, *nread);
   }
   
   return request_len <= 0 && n <= 0 ? -1 : request_len;
}

// For given directory path, substitute it to valid index file.
// Return 0 if index file has been found, -1 if not found.
// If the file is found, it's stats is returned in stp.
static int substitute_index_file(struct mg_connection *conn, char *path,
                                 size_t path_len, struct file *filep) {
   const char *list = conn->ctx->config[INDEX_FILES];
   struct file file = STRUCT_FILE_INITIALIZER;
   struct vec filename_vec;
   size_t n = strlen(path);
   int found = 0;
   
   // The 'path' given to us points to the directory. Remove all trailing
   // directory separator characters from the end of the path, and
   // then append single directory separator character.
   while (n > 0 && path[n - 1] == '/') {
      n--;
   }
   path[n] = '/';
   
   // Traverse index files list. For each entry, append it to the given
   // path and see if the file exists. If it exists, break the loop
   while ((list = next_option(list, &filename_vec, NULL)) != NULL) {
      
      // Ignore too long entries that may overflow path buffer
      if (filename_vec.len > path_len - (n + 2))
         continue;
      
      // Prepare full path to the index file
      mg_strlcpy(path + n + 1, filename_vec.ptr, filename_vec.len + 1);
      
      // Does it exist?
      if (mg_stat(conn, path, &file)) {
         // Yes it does, break the loop
         *filep = file;
         found = 1;
         break;
      }
   }
   
   // If no index file exists, restore directory path
   if (!found) {
      path[n] = '\0';
   }
   
   return found;
}

// Return True if we should reply 304 Not Modified.
static int is_not_modified(const struct mg_connection *conn,
                           const struct file *filep) {
   char etag[64];
   const char *ims = mg_get_header(conn, "If-Modified-Since");
   const char *inm = mg_get_header(conn, "If-None-Match");
   construct_etag(etag, sizeof(etag), filep);
   return (inm != NULL && !mg_strcasecmp(etag, inm)) ||
   (ims != NULL && filep->modification_time <= parse_date_string(ims));
}

static int forward_body_data(struct mg_connection *conn, FILE *fp,
                             SOCKET sock, SSL *ssl) {
   const char *expect, *body;
   char buf[MG_BUF_LEN];
   int to_read, nread, buffered_len, success = 0;
   
   expect = mg_get_header(conn, "Expect");
   assert(fp != NULL);
   
   if (conn->content_len == -1) {
      send_http_error(conn, 411, "Length Required", "%s", "");
   } else if (expect != NULL && mg_strcasecmp(expect, "100-continue")) {
      send_http_error(conn, 417, "Expectation Failed", "%s", "");
   } else {
      if (expect != NULL) {
         (void) mg_printf(conn, "%s", "HTTP/1.1 100 Continue\r\n\r\n");
      }
      
      body = conn->buf + conn->request_len + conn->consumed_content;
      buffered_len = &conn->buf[conn->data_len] - body;
      assert(buffered_len >= 0);
      assert(conn->consumed_content == 0);
      
      if (buffered_len > 0) {
         if ((int64_t) buffered_len > conn->content_len) {
            buffered_len = (int) conn->content_len;
         }
         push(fp, sock, ssl, body, (int64_t) buffered_len);
         conn->consumed_content += buffered_len;
      }
      
      nread = 0;
      while (conn->consumed_content < conn->content_len) {
         to_read = sizeof(buf);
         if ((int64_t) to_read > conn->content_len - conn->consumed_content) {
            to_read = (int) (conn->content_len - conn->consumed_content);
         }
         nread = pull(NULL, conn, buf, to_read);
         if (nread <= 0 || push(fp, sock, ssl, buf, nread) != nread) {
            break;
         }
         conn->consumed_content += nread;
      }
      
      if (conn->consumed_content == conn->content_len) {
         success = nread >= 0;
      }
      
      // Each error code path in this function must send an error
      if (!success) {
         send_http_error(conn, 577, http_500_error, "%s", "");
      }
   }
   
   return success;
}

#if !defined(NO_CGI)
// This structure helps to create an environment for the spawned CGI program.
// Environment is an array of "VARIABLE=VALUE\0" ASCIIZ strings,
// last element must be NULL.
// However, on Windows there is a requirement that all these VARIABLE=VALUE\0
// strings must reside in a contiguous buffer. The end of the buffer is
// marked by two '\0' characters.
// We satisfy both worlds: we create an envp array (which is vars), all
// entries are actually pointers inside buf.
struct cgi_env_block {
   struct mg_connection *conn;
   char buf[CGI_ENVIRONMENT_SIZE]; // Environment buffer
   int len; // Space taken
   char *vars[MAX_CGI_ENVIR_VARS]; // char **envp
   int nvars; // Number of variables
};

static char *addenv(struct cgi_env_block *block,
                    PRINTF_FORMAT_STRING(const char *fmt), ...)
PRINTF_ARGS(2, 3);

// Append VARIABLE=VALUE\0 string to the buffer, and add a respective
// pointer into the vars array.
static char *addenv(struct cgi_env_block *block, const char *fmt, ...) {
   int n, space;
   char *added;
   va_list ap;
   
   // Calculate how much space is left in the buffer
   space = sizeof(block->buf) - block->len - 2;
   assert(space >= 0);
   
   // Make a pointer to the free space int the buffer
   added = block->buf + block->len;
   
   // Copy VARIABLE=VALUE\0 string into the free space
   va_start(ap, fmt);
   n = mg_vsnprintf(block->conn, added, (size_t) space, fmt, ap);
   va_end(ap);
   
   // Make sure we do not overflow buffer and the envp array
   if (n > 0 && n + 1 < space &&
       block->nvars < (int) ARRAY_SIZE(block->vars) - 2) {
      // Append a pointer to the added string into the envp array
      block->vars[block->nvars++] = added;
      // Bump up used length counter. Include \0 terminator
      block->len += n + 1;
   } else {
      cry(block->conn, "%s: CGI env buffer truncated for [%s]", __func__, fmt);
   }
   
   return added;
}

static void prepare_cgi_environment(struct mg_connection *conn,
                                    const char *prog,
                                    struct cgi_env_block *blk) {
   const char *s, *slash;
   struct vec var_vec;
   char *p, src_addr[20];
   int  i;
   
   blk->len = blk->nvars = 0;
   blk->conn = conn;
   sockaddr_to_string(src_addr, sizeof(src_addr), &conn->client.rsa);
   
   addenv(blk, "SERVER_NAME=%s", conn->ctx->config[AUTHENTICATION_DOMAIN]);
   addenv(blk, "SERVER_ROOT=%s", conn->ctx->config[DOCUMENT_ROOT]);
   addenv(blk, "DOCUMENT_ROOT=%s", conn->ctx->config[DOCUMENT_ROOT]);
   
   // Prepare the environment block
   addenv(blk, "%s", "GATEWAY_INTERFACE=CGI/1.1");
   addenv(blk, "%s", "SERVER_PROTOCOL=HTTP/1.1");
   addenv(blk, "%s", "REDIRECT_STATUS=200"); // For PHP
   
   // TODO(lsm): fix this for IPv6 case
   addenv(blk, "SERVER_PORT=%d", ntohs(conn->client.lsa.sin.sin_port));
   
   addenv(blk, "REQUEST_METHOD=%s", conn->request_info.request_method);
   addenv(blk, "REMOTE_ADDR=%s", src_addr);
   addenv(blk, "REMOTE_PORT=%d", conn->request_info.remote_port);
   addenv(blk, "REQUEST_URI=%s", conn->request_info.uri);
   
   // SCRIPT_NAME
   assert(conn->request_info.uri[0] == '/');
   slash = strrchr(conn->request_info.uri, '/');
   if ((s = strrchr(prog, '/')) == NULL)
      s = prog;
   addenv(blk, "SCRIPT_NAME=%.*s%s", (int) (slash - conn->request_info.uri),
          conn->request_info.uri, s);
   
   addenv(blk, "SCRIPT_FILENAME=%s", prog);
   addenv(blk, "PATH_TRANSLATED=%s", prog);
   addenv(blk, "HTTPS=%s", conn->ssl == NULL ? "off" : "on");
   
   if ((s = mg_get_header(conn, "Content-Type")) != NULL)
      addenv(blk, "CONTENT_TYPE=%s", s);
   
   if (conn->request_info.query_string != NULL)
      addenv(blk, "QUERY_STRING=%s", conn->request_info.query_string);
   
   if ((s = mg_get_header(conn, "Content-Length")) != NULL)
      addenv(blk, "CONTENT_LENGTH=%s", s);
   
   if ((s = getenv("PATH")) != NULL)
      addenv(blk, "PATH=%s", s);
   
   if (conn->path_info != NULL) {
      addenv(blk, "PATH_INFO=%s", conn->path_info);
   }
   
#if defined(_WIN32)
   if ((s = getenv("COMSPEC")) != NULL) {
      addenv(blk, "COMSPEC=%s", s);
   }
   if ((s = getenv("SYSTEMROOT")) != NULL) {
      addenv(blk, "SYSTEMROOT=%s", s);
   }
   if ((s = getenv("SystemDrive")) != NULL) {
      addenv(blk, "SystemDrive=%s", s);
   }
   if ((s = getenv("ProgramFiles")) != NULL) {
      addenv(blk, "ProgramFiles=%s", s);
   }
   if ((s = getenv("ProgramFiles(x86)")) != NULL) {
      addenv(blk, "ProgramFiles(x86)=%s", s);
   }
#else
   if ((s = getenv("LD_LIBRARY_PATH")) != NULL)
      addenv(blk, "LD_LIBRARY_PATH=%s", s);
#endif // _WIN32
   
   if ((s = getenv("PERLLIB")) != NULL)
      addenv(blk, "PERLLIB=%s", s);
   
   if (conn->request_info.remote_user != NULL) {
      addenv(blk, "REMOTE_USER=%s", conn->request_info.remote_user);
      addenv(blk, "%s", "AUTH_TYPE=Digest");
   }
   
   // Add all headers as HTTP_* variables
   for (i = 0; i < conn->request_info.num_headers; i++) {
      p = addenv(blk, "HTTP_%s=%s",
                 conn->request_info.http_headers[i].name,
                 conn->request_info.http_headers[i].value);
      
      // Convert variable name into uppercase, and change - to _
      for (; *p != '=' && *p != '\0'; p++) {
         if (*p == '-')
            *p = '_';
         *p = (char) toupper(* (unsigned char *) p);
      }
   }
   
   // Add user-specified variables
   s = conn->ctx->config[CGI_ENVIRONMENT];
   while ((s = next_option(s, &var_vec, NULL)) != NULL) {
      addenv(blk, "%.*s", (int) var_vec.len, var_vec.ptr);
   }
   
   blk->vars[blk->nvars++] = NULL;
   blk->buf[blk->len++] = '\0';
   
   assert(blk->nvars < (int) ARRAY_SIZE(blk->vars));
   assert(blk->len > 0);
   assert(blk->len < (int) sizeof(blk->buf));
/*
   for(int i=0;i<blk->nvars;i++)
      printf("CGI : %s\n",blk->vars[i]);
*/
}

static void handle_cgi_request(struct mg_connection *conn, const char *prog) {
   int headers_len, data_len, i, fd_stdin[2], fd_stdout[2];
   const char *status, *status_text;
   char buf[16384], *pbuf, dir[PATH_MAX], *p;
   struct mg_request_info ri;
   struct cgi_env_block blk;
   FILE *in, *out;
   struct file fout = STRUCT_FILE_INITIALIZER;
   pid_t pid;
   
   prepare_cgi_environment(conn, prog, &blk);
   
   // CGI must be executed in its own directory. 'dir' must point to the
   // directory containing executable program, 'p' must point to the
   // executable program name relative to 'dir'.
   (void) mg_snprintf(conn, dir, sizeof(dir), "%s", prog);
   if ((p = strrchr(dir, '/')) != NULL) {
      *p++ = '\0';
   } else {
      dir[0] = '.', dir[1] = '\0';
      p = (char *) prog;
   }
   
   pid = (pid_t) -1;
   fd_stdin[0] = fd_stdin[1] = fd_stdout[0] = fd_stdout[1] = -1;
   in = out = NULL;
   
   if (pipe(fd_stdin) != 0 || pipe(fd_stdout) != 0) {
      send_http_error(conn, 500, http_500_error,
                      "Cannot create CGI pipe: %s", strerror(ERRNO));
      goto done;
   }
   
   pid = spawn_process(conn, p, blk.buf, blk.vars, fd_stdin[0], fd_stdout[1],
                       dir);
   // spawn_process() must close those!
   // If we don't mark them as closed, close() attempt before
   // return from this function throws an exception on Windows.
   // Windows does not like when closed descriptor is closed again.
   fd_stdin[0] = fd_stdout[1] = -1;
   
   if (pid == (pid_t) -1) {
      send_http_error(conn, 500, http_500_error,
                      "Cannot spawn CGI process [%s]: %s", prog, strerror(ERRNO));
      goto done;
   }
   
   if ((in = fdopen(fd_stdin[1], "wb")) == NULL ||
       (out = fdopen(fd_stdout[0], "rb")) == NULL) {
      send_http_error(conn, 500, http_500_error,
                      "fopen: %s", strerror(ERRNO));
      goto done;
   }
   
   setbuf(in, NULL);
   setbuf(out, NULL);
   fout.fp = out;
   
   // Send POST data to the CGI process if needed
   if (!strcmp(conn->request_info.request_method, "POST") &&
       !forward_body_data(conn, in, INVALID_SOCKET, NULL)) {
      goto done;
   }
   
   // Close so child gets an EOF.
   fclose(in);
   in = NULL;
   fd_stdin[1] = -1;
   
   // Now read CGI reply into a buffer. We need to set correct
   // status code, thus we need to see all HTTP headers first.
   // Do not send anything back to client, until we buffer in all
   // HTTP headers.
   data_len = 0;
   headers_len = read_request(out, conn, buf, sizeof(buf), &data_len);
   if (headers_len <= 0) {
      send_http_error(conn, 500, http_500_error,
                      "CGI program sent malformed or too big (>%u bytes) "
                      "HTTP headers: [%.*s]",
                      (unsigned) sizeof(buf), data_len, buf);
      goto done;
   }
   pbuf = buf;
   buf[headers_len - 1] = '\0';
   parse_http_headers(&pbuf, &ri);
   
   // Make up and send the status line
   status_text = "OK";
   if ((status = get_header(&ri, "Status")) != NULL) {
      conn->status_code = atoi(status);
      status_text = status;
      while (isdigit(* (unsigned char *) status_text) || *status_text == ' ') {
         status_text++;
      }
   } else if (get_header(&ri, "Location") != NULL) {
      conn->status_code = 302;
   } else {
      conn->status_code = 200;
   }
   if (get_header(&ri, "Connection") != NULL &&
       !mg_strcasecmp(get_header(&ri, "Connection"), "keep-alive")) {
      conn->must_close = 1;
   }
   (void) mg_printf(conn, "HTTP/1.1 %d %s\r\n", conn->status_code,
                    status_text);
   
   // Send headers
   for (i = 0; i < ri.num_headers; i++) {
      mg_printf(conn, "%s: %s\r\n",
                ri.http_headers[i].name, ri.http_headers[i].value);
   }
   mg_write(conn, "\r\n", 2);
   
   // Send chunk of data that may have been read after the headers
   conn->num_bytes_sent += mg_write(conn, buf + headers_len,
                                    (size_t)(data_len - headers_len));
   
   // Read the rest of CGI output and send to the client
   send_file_data(conn, &fout, 0, INT64_MAX);
   
done:
   if (pid != (pid_t) -1) {
      kill(pid, SIGKILL);
   }
   if (fd_stdin[0] != -1) {
      close(fd_stdin[0]);
   }
   if (fd_stdout[1] != -1) {
      close(fd_stdout[1]);
   }
   
   if (in != NULL) {
      fclose(in);
   } else if (fd_stdin[1] != -1) {
      close(fd_stdin[1]);
   }
   
   if (out != NULL) {
      fclose(out);
   } else if (fd_stdout[0] != -1) {
      close(fd_stdout[0]);
   }
}
#endif // !NO_CGI

// For a given PUT path, create all intermediate subdirectories
// for given path. Return 0 if the path itself is a directory,
// or -1 on error, 1 if OK.
static int put_dir(struct mg_connection *conn, const char *path) {
   char buf[PATH_MAX];
   const char *s, *p;
   struct file file = STRUCT_FILE_INITIALIZER;
   int len, res = 1;
   
   for (s = p = path + 2; (p = strchr(s, '/')) != NULL; s = ++p) {
      len = p - path;
      if (len >= (int) sizeof(buf)) {
         res = -1;
         break;
      }
      memcpy(buf, path, len);
      buf[len] = '\0';
      
      // Try to create intermediate directory
      DEBUG_TRACE(("mkdir(%s)", buf));
      if (!mg_stat(conn, buf, &file) && mg_mkdir(buf, 0755) != 0) {
         res = -1;
         break;
      }
      
      // Is path itself a directory?
      if (p[1] == '\0') {
         res = 0;
      }
   }
   
   return res;
}

static void put_file(struct mg_connection *conn, const char *path) {
   struct file file = STRUCT_FILE_INITIALIZER;
   const char *range;
   int64_t r1, r2;
   int rc;
   
   conn->status_code = mg_stat(conn, path, &file) ? 200 : 201;
   
   if ((rc = put_dir(conn, path)) == 0) {
      mg_printf(conn, "HTTP/1.1 %d OK\r\n\r\n", conn->status_code);
   } else if (rc == -1) {
      send_http_error(conn, 500, http_500_error,
                      "put_dir(%s): %s", path, strerror(ERRNO));
   } else if (!mg_fopen(conn, path, "wb+", &file) || file.fp == NULL) {
      mg_fclose(&file);
      send_http_error(conn, 500, http_500_error,
                      "fopen(%s): %s", path, strerror(ERRNO));
   } else {
      fclose_on_exec(&file);
      range = mg_get_header(conn, "Content-Range");
      r1 = r2 = 0;
      if (range != NULL && parse_range_header(range, &r1, &r2) > 0) {
         conn->status_code = 206;
         fseeko(file.fp, r1, SEEK_SET);
      }
      if (forward_body_data(conn, file.fp, INVALID_SOCKET, NULL)) {
         mg_printf(conn, "HTTP/1.1 %d OK\r\n\r\n", conn->status_code);
      }
      mg_fclose(&file);
   }
}

static void send_ssi_file(struct mg_connection *, const char *,
                          struct file *, int);

static void do_ssi_include(struct mg_connection *conn, const char *ssi,
                           char *tag, int include_level) {
   char file_name[MG_BUF_LEN], path[PATH_MAX], *p;
   struct file file = STRUCT_FILE_INITIALIZER;
   
   // sscanf() is safe here, since send_ssi_file() also uses buffer
   // of size MG_BUF_LEN to get the tag. So strlen(tag) is always < MG_BUF_LEN.
   if (sscanf(tag, " virtual=\"%[^\"]\"", file_name) == 1) {
      // File name is relative to the webserver root
      (void) mg_snprintf(conn, path, sizeof(path), "%s%c%s",
                         conn->ctx->config[DOCUMENT_ROOT], '/', file_name);
   } else if (sscanf(tag, " file=\"%[^\"]\"", file_name) == 1) {
      // File name is relative to the webserver working directory
      // or it is absolute system path
      (void) mg_snprintf(conn, path, sizeof(path), "%s", file_name);
   } else if (sscanf(tag, " \"%[^\"]\"", file_name) == 1) {
      // File name is relative to the currect document
      (void) mg_snprintf(conn, path, sizeof(path), "%s", ssi);
      if ((p = strrchr(path, '/')) != NULL) {
         p[1] = '\0';
      }
      (void) mg_snprintf(conn, path + strlen(path),
                         sizeof(path) - strlen(path), "%s", file_name);
   } else {
      cry(conn, "Bad SSI #include: [%s]", tag);
      return;
   }
   
   if (!mg_fopen(conn, path, "rb", &file)) {
      cry(conn, "Cannot open SSI #include: [%s]: fopen(%s): %s",
          tag, path, strerror(ERRNO));
   } else {
      fclose_on_exec(&file);
      if (match_prefix(conn->ctx->config[SSI_EXTENSIONS],
                       strlen(conn->ctx->config[SSI_EXTENSIONS]), path) > 0) {
         send_ssi_file(conn, path, &file, include_level + 1);
      } else {
         send_file_data(conn, &file, 0, INT64_MAX);
      }
      mg_fclose(&file);
   }
}

#if !defined(NO_POPEN)
static void do_ssi_exec(struct mg_connection *conn, char *tag) {
   char cmd[MG_BUF_LEN];
   struct file file = STRUCT_FILE_INITIALIZER;
   
   if (sscanf(tag, " \"%[^\"]\"", cmd) != 1) {
      cry(conn, "Bad SSI #exec: [%s]", tag);
   } else if ((file.fp = popen(cmd, "r")) == NULL) {
      cry(conn, "Cannot SSI #exec: [%s]: %s", cmd, strerror(ERRNO));
   } else {
      send_file_data(conn, &file, 0, INT64_MAX);
      pclose(file.fp);
   }
}
#endif // !NO_POPEN

static int mg_fgetc(struct file *filep, int offset) {
   if (filep->membuf != NULL && offset >=0 && offset < filep->size) {
      return ((unsigned char *) filep->membuf)[offset];
   } else if (filep->fp != NULL) {
      return fgetc(filep->fp);
   } else {
      return EOF;
   }
}

static void send_ssi_file(struct mg_connection *conn, const char *path,
                          struct file *filep, int include_level) {
   char buf[MG_BUF_LEN];
   int ch, offset, len, in_ssi_tag;
   
   if (include_level > 10) {
      cry(conn, "SSI #include level is too deep (%s)", path);
      return;
   }
   
   in_ssi_tag = len = offset = 0;
   while ((ch = mg_fgetc(filep, offset)) != EOF) {
      if (in_ssi_tag && ch == '>') {
         in_ssi_tag = 0;
         buf[len++] = (char) ch;
         buf[len] = '\0';
         assert(len <= (int) sizeof(buf));
         if (len < 6 || memcmp(buf, "<!--#", 5) != 0) {
            // Not an SSI tag, pass it
            (void) mg_write(conn, buf, (size_t) len);
         } else {
            if (!memcmp(buf + 5, "include", 7)) {
               do_ssi_include(conn, path, buf + 12, include_level);
#if !defined(NO_POPEN)
            } else if (!memcmp(buf + 5, "exec", 4)) {
               do_ssi_exec(conn, buf + 9);
#endif // !NO_POPEN
            } else {
               cry(conn, "%s: unknown SSI " "command: \"%s\"", path, buf);
            }
         }
         len = 0;
      } else if (in_ssi_tag) {
         if (len == 5 && memcmp(buf, "<!--#", 5) != 0) {
            // Not an SSI tag
            in_ssi_tag = 0;
         } else if (len == (int) sizeof(buf) - 2) {
            cry(conn, "%s: SSI tag is too large", path);
            len = 0;
         }
         buf[len++] = ch & 0xff;
      } else if (ch == '<') {
         in_ssi_tag = 1;
         if (len > 0) {
            mg_write(conn, buf, (size_t) len);
         }
         len = 0;
         buf[len++] = ch & 0xff;
      } else {
         buf[len++] = ch & 0xff;
         if (len == (int) sizeof(buf)) {
            mg_write(conn, buf, (size_t) len);
            len = 0;
         }
      }
   }
   
   // Send the rest of buffered data
   if (len > 0) {
      mg_write(conn, buf, (size_t) len);
   }
}

static void handle_ssi_file_request(struct mg_connection *conn,
                                    const char *path) {
   struct file file = STRUCT_FILE_INITIALIZER;
   
   if (!mg_fopen(conn, path, "rb", &file)) {
      send_http_error(conn, 500, http_500_error, "fopen(%s): %s", path,
                      strerror(ERRNO));
   } else {
      conn->must_close = 1;
      fclose_on_exec(&file);
      mg_printf(conn, "HTTP/1.1 200 OK\r\n"
                "Content-Type: text/html\r\nConnection: %s\r\n\r\n",
                suggest_connection_header(conn));
      send_ssi_file(conn, path, &file, 0);
      mg_fclose(&file);
   }
}

static void send_options(struct mg_connection *conn) {
   conn->status_code = 200;
   
   mg_printf(conn, "%s", "HTTP/1.1 200 OK\r\n"
             "Allow: GET, POST, HEAD, CONNECT, PUT, DELETE, OPTIONS\r\n"
             "DAV: 1\r\n\r\n");
}

// Writes PROPFIND properties for a collection element
static void print_props(struct mg_connection *conn, const char* uri,
                        struct file *filep) {
   char mtime[64];
   gmt_time_string(mtime, sizeof(mtime), &filep->modification_time);
   conn->num_bytes_sent += mg_printf(conn,
                                     "<d:response>"
                                     "<d:href>%s</d:href>"
                                     "<d:propstat>"
                                     "<d:prop>"
                                     "<d:resourcetype>%s</d:resourcetype>"
                                     "<d:getcontentlength>%" INT64_FMT "</d:getcontentlength>"
                                     "<d:getlastmodified>%s</d:getlastmodified>"
                                     "</d:prop>"
                                     "<d:status>HTTP/1.1 200 OK</d:status>"
                                     "</d:propstat>"
                                     "</d:response>\n",
                                     uri,
                                     filep->is_directory ? "<d:collection/>" : "",
                                     filep->size,
                                     mtime);
}

static void print_dav_dir_entry(struct de *de, void *data) {
   char href[PATH_MAX];
   struct mg_connection *conn = (struct mg_connection *) data;
   mg_snprintf(conn, href, sizeof(href), "%s%s",
               conn->request_info.uri, de->file_name);
   print_props(conn, href, &de->file);
}

static void handle_propfind(struct mg_connection *conn, const char *path,
                            struct file *filep) {
   const char *depth = mg_get_header(conn, "Depth");
   
   conn->must_close = 1;
   conn->status_code = 207;
   mg_printf(conn, "HTTP/1.1 207 Multi-Status\r\n"
             "Connection: close\r\n"
             "Content-Type: text/xml; charset=utf-8\r\n\r\n");
   
   conn->num_bytes_sent += mg_printf(conn,
                                     "<?xml version=\"1.0\" encoding=\"utf-8\"?>"
                                     "<d:multistatus xmlns:d='DAV:'>\n");
   
   // Print properties for the requested resource itself
   print_props(conn, conn->request_info.uri, filep);
   
   // If it is a directory, print directory entries too if Depth is not 0
   if (filep->is_directory &&
       !mg_strcasecmp(conn->ctx->config[ENABLE_DIRECTORY_LISTING], "yes") &&
       (depth == NULL || strcmp(depth, "0") != 0)) {
      scan_directory(conn, path, conn, &print_dav_dir_entry);
   }
   
   conn->num_bytes_sent += mg_printf(conn, "%s\n", "</d:multistatus>");
}

#if defined(USE_WEBSOCKET)

// START OF SHA-1 code
// Copyright(c) By Steve Reid <steve@edmweb.com>
#define SHA1HANDSOFF
#if defined(__sun)
#include "solarisfixes.h"
#endif

union char64long16 { unsigned char c[64]; uint32_t l[16]; };

#define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))

static uint32_t blk0(union char64long16 *block, int i) {
   // Forrest: SHA expect BIG_ENDIAN, swap if LITTLE_ENDIAN
   if (!is_big_endian()) {
      block->l[i] = (rol(block->l[i], 24) & 0xFF00FF00) |
      (rol(block->l[i], 8) & 0x00FF00FF);
   }
   return block->l[i];
}

#define blk(i) (block->l[i&15] = rol(block->l[(i+13)&15]^block->l[(i+8)&15] \
^block->l[(i+2)&15]^block->l[i&15],1))
#define R0(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk0(block, i)+0x5A827999+rol(v,5);w=rol(w,30);
#define R1(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk(i)+0x5A827999+rol(v,5);w=rol(w,30);
#define R2(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0x6ED9EBA1+rol(v,5);w=rol(w,30);
#define R3(v,w,x,y,z,i) z+=(((w|x)&y)|(w&x))+blk(i)+0x8F1BBCDC+rol(v,5);w=rol(w,30);
#define R4(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0xCA62C1D6+rol(v,5);w=rol(w,30);

typedef struct {
   uint32_t state[5];
   uint32_t count[2];
   unsigned char buffer[64];
} SHA1_CTX;

static void SHA1Transform(uint32_t state[5], const unsigned char buffer[64]) {
   uint32_t a, b, c, d, e;
   union char64long16 block[1];
   
   memcpy(block, buffer, 64);
   a = state[0];
   b = state[1];
   c = state[2];
   d = state[3];
   e = state[4];
   R0(a,b,c,d,e, 0); R0(e,a,b,c,d, 1); R0(d,e,a,b,c, 2); R0(c,d,e,a,b, 3);
   R0(b,c,d,e,a, 4); R0(a,b,c,d,e, 5); R0(e,a,b,c,d, 6); R0(d,e,a,b,c, 7);
   R0(c,d,e,a,b, 8); R0(b,c,d,e,a, 9); R0(a,b,c,d,e,10); R0(e,a,b,c,d,11);
   R0(d,e,a,b,c,12); R0(c,d,e,a,b,13); R0(b,c,d,e,a,14); R0(a,b,c,d,e,15);
   R1(e,a,b,c,d,16); R1(d,e,a,b,c,17); R1(c,d,e,a,b,18); R1(b,c,d,e,a,19);
   R2(a,b,c,d,e,20); R2(e,a,b,c,d,21); R2(d,e,a,b,c,22); R2(c,d,e,a,b,23);
   R2(b,c,d,e,a,24); R2(a,b,c,d,e,25); R2(e,a,b,c,d,26); R2(d,e,a,b,c,27);
   R2(c,d,e,a,b,28); R2(b,c,d,e,a,29); R2(a,b,c,d,e,30); R2(e,a,b,c,d,31);
   R2(d,e,a,b,c,32); R2(c,d,e,a,b,33); R2(b,c,d,e,a,34); R2(a,b,c,d,e,35);
   R2(e,a,b,c,d,36); R2(d,e,a,b,c,37); R2(c,d,e,a,b,38); R2(b,c,d,e,a,39);
   R3(a,b,c,d,e,40); R3(e,a,b,c,d,41); R3(d,e,a,b,c,42); R3(c,d,e,a,b,43);
   R3(b,c,d,e,a,44); R3(a,b,c,d,e,45); R3(e,a,b,c,d,46); R3(d,e,a,b,c,47);
   R3(c,d,e,a,b,48); R3(b,c,d,e,a,49); R3(a,b,c,d,e,50); R3(e,a,b,c,d,51);
   R3(d,e,a,b,c,52); R3(c,d,e,a,b,53); R3(b,c,d,e,a,54); R3(a,b,c,d,e,55);
   R3(e,a,b,c,d,56); R3(d,e,a,b,c,57); R3(c,d,e,a,b,58); R3(b,c,d,e,a,59);
   R4(a,b,c,d,e,60); R4(e,a,b,c,d,61); R4(d,e,a,b,c,62); R4(c,d,e,a,b,63);
   R4(b,c,d,e,a,64); R4(a,b,c,d,e,65); R4(e,a,b,c,d,66); R4(d,e,a,b,c,67);
   R4(c,d,e,a,b,68); R4(b,c,d,e,a,69); R4(a,b,c,d,e,70); R4(e,a,b,c,d,71);
   R4(d,e,a,b,c,72); R4(c,d,e,a,b,73); R4(b,c,d,e,a,74); R4(a,b,c,d,e,75);
   R4(e,a,b,c,d,76); R4(d,e,a,b,c,77); R4(c,d,e,a,b,78); R4(b,c,d,e,a,79);
   state[0] += a;
   state[1] += b;
   state[2] += c;
   state[3] += d;
   state[4] += e;
   a = b = c = d = e = 0;
   memset(block, '\0', sizeof(block));
}

static void SHA1Init(SHA1_CTX* context) {
   context->state[0] = 0x67452301;
   context->state[1] = 0xEFCDAB89;
   context->state[2] = 0x98BADCFE;
   context->state[3] = 0x10325476;
   context->state[4] = 0xC3D2E1F0;
   context->count[0] = context->count[1] = 0;
}

static void SHA1Update(SHA1_CTX* context, const unsigned char* data,
                       uint32_t len) {
   uint32_t i, j;
   
   j = context->count[0];
   if ((context->count[0] += len << 3) < j)
      context->count[1]++;
   context->count[1] += (len>>29);
   j = (j >> 3) & 63;
   if ((j + len) > 63) {
      memcpy(&context->buffer[j], data, (i = 64-j));
      SHA1Transform(context->state, context->buffer);
      for ( ; i + 63 < len; i += 64) {
         SHA1Transform(context->state, &data[i]);
      }
      j = 0;
   }
   else i = 0;
   memcpy(&context->buffer[j], &data[i], len - i);
}

static void SHA1Final(unsigned char digest[20], SHA1_CTX* context) {
   unsigned i;
   unsigned char finalcount[8], c;
   
   for (i = 0; i < 8; i++) {
      finalcount[i] = (unsigned char)((context->count[(i >= 4 ? 0 : 1)]
                                       >> ((3-(i & 3)) * 8) ) & 255);
   }
   c = 0200;
   SHA1Update(context, &c, 1);
   while ((context->count[0] & 504) != 448) {
      c = 0000;
      SHA1Update(context, &c, 1);
   }
   SHA1Update(context, finalcount, 8);
   for (i = 0; i < 20; i++) {
      digest[i] = (unsigned char)
      ((context->state[i>>2] >> ((3-(i & 3)) * 8) ) & 255);
   }
   memset(context, '\0', sizeof(*context));
   memset(&finalcount, '\0', sizeof(finalcount));
}
// END OF SHA1 CODE

static void base64_encode(const unsigned char *src, int src_len, char *dst) {
   static const char *b64 =
   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
   int i, j, a, b, c;
   
   for (i = j = 0; i < src_len; i += 3) {
      a = src[i];
      b = i + 1 >= src_len ? 0 : src[i + 1];
      c = i + 2 >= src_len ? 0 : src[i + 2];
      
      dst[j++] = b64[a >> 2];
      dst[j++] = b64[((a & 3) << 4) | (b >> 4)];
      if (i + 1 < src_len) {
         dst[j++] = b64[(b & 15) << 2 | (c >> 6)];
      }
      if (i + 2 < src_len) {
         dst[j++] = b64[c & 63];
      }
   }
   while (j % 4 != 0) {
      dst[j++] = '=';
   }
   dst[j++] = '\0';
}

static void send_websocket_handshake(struct mg_connection *conn) {
   static const char *magic = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
   char buf[100], sha[20], b64_sha[sizeof(sha) * 2];
   SHA1_CTX sha_ctx;
   
   mg_snprintf(conn, buf, sizeof(buf), "%s%s",
               mg_get_header(conn, "Sec-WebSocket-Key"), magic);
   SHA1Init(&sha_ctx);
   SHA1Update(&sha_ctx, (unsigned char *) buf, strlen(buf));
   SHA1Final((unsigned char *) sha, &sha_ctx);
   base64_encode((unsigned char *) sha, sizeof(sha), b64_sha);
   mg_printf(conn, "%s%s%s",
             "HTTP/1.1 101 Switching Protocols\r\n"
             "Upgrade: websocket\r\n"
             "Connection: Upgrade\r\n"
             "Sec-WebSocket-Accept: ", b64_sha, "\r\n\r\n");
}

static void read_websocket(struct mg_connection *conn) {
   unsigned char *buf = (unsigned char *) conn->buf + conn->request_len;
   int bits, n, stop = 0;
   size_t i, len, mask_len, data_len, header_len, body_len;
   char mem[4 * 1024], mask[4], *data;
   
   assert(conn->content_len == 0);
   while (!stop) {
      header_len = 0;
      if ((body_len = conn->data_len - conn->request_len) >= 2) {
         len = buf[1] & 127;
         mask_len = buf[1] & 128 ? 4 : 0;
         if (len < 126 && body_len >= mask_len) {
            data_len = len;
            header_len = 2 + mask_len;
         } else if (len == 126 && body_len >= 4 + mask_len) {
            header_len = 4 + mask_len;
            data_len = ((((int) buf[2]) << 8) + buf[3]);
         } else if (body_len >= 10 + mask_len) {
            header_len = 10 + mask_len;
            data_len = (((uint64_t) htonl(* (uint32_t *) &buf[2])) << 32) +
            htonl(* (uint32_t *) &buf[6]);
         }
      }
      
      // Data layout is as follows:
      //  conn->buf               buf
      //     v                     v              frame1           | frame2
      //     |---------------------|----------------|--------------|-------
      //     |                     |<--header_len-->|<--data_len-->|
      //     |<-conn->request_len->|<-----body_len----------->|
      //     |<-------------------conn->data_len------------->|
      
      if (header_len > 0) {
         // Allocate space to hold websocket payload
         data = mem;
         if (data_len > sizeof(mem) && (data = malloc(data_len)) == NULL) {
            // Allocation failed, exit the loop and then close the connection
            // TODO: notify user about the failure
            break;
         }
         
         // Save mask and bits, otherwise it may be clobbered by memmove below
         bits = buf[0];
         memcpy(mask, buf + header_len - mask_len, mask_len);
         
         // Read frame payload into the allocated buffer.
         assert(body_len >= header_len);
         if (data_len + header_len > body_len) {
            len = body_len - header_len;
            memcpy(data, buf + header_len, len);
            // TODO: handle pull error
            pull_all(NULL, conn, data + len, data_len - len);
            conn->data_len = conn->request_len;
         } else {
            len = data_len + header_len;
            memcpy(data, buf + header_len, data_len);
            memmove(buf, buf + len, body_len - len);
            conn->data_len -= len;
         }
         
         // Apply mask if necessary
         if (mask_len > 0) {
            for (i = 0; i < data_len; i++) {
               data[i] ^= mask[i % 4];
            }
         }
         
         // Exit the loop if callback signalled to exit,
         // or "connection close" opcode received.
         if ((conn->ctx->callbacks.websocket_data != NULL &&
              !conn->ctx->callbacks.websocket_data(conn, bits, data, data_len)) ||
             (bits & 0xf) == 8) {  // Opcode == 8, connection close
            stop = 1;
         }
         
         if (data != mem) {
            free(data);
         }
         // Not breaking the loop, process next websocket frame.
      } else {
         // Buffering websocket request
         if ((n = pull(NULL, conn, conn->buf + conn->data_len,
                       conn->buf_size - conn->data_len)) <= 0) {
            break;
         }
         conn->data_len += n;
      }
   }
}

static void handle_websocket_request(struct mg_connection *conn) {
   const char *version = mg_get_header(conn, "Sec-WebSocket-Version");
   if (version == NULL || strcmp(version, "13") != 0) {
      send_http_error(conn, 426, "Upgrade Required", "%s", "Upgrade Required");
   } else if (conn->ctx->callbacks.websocket_connect != NULL &&
              conn->ctx->callbacks.websocket_connect(conn) != 0) {
      // Callback has returned non-zero, do not proceed with handshake
   } else {
      send_websocket_handshake(conn);
      if (conn->ctx->callbacks.websocket_ready != NULL) {
         conn->ctx->callbacks.websocket_ready(conn);
      }
      read_websocket(conn);
   }
}

static int is_websocket_request(const struct mg_connection *conn) {
   const char *host, *upgrade, *connection, *version, *key;
   
   host = mg_get_header(conn, "Host");
   upgrade = mg_get_header(conn, "Upgrade");
   connection = mg_get_header(conn, "Connection");
   key = mg_get_header(conn, "Sec-WebSocket-Key");
   version = mg_get_header(conn, "Sec-WebSocket-Version");
   
   return host != NULL && upgrade != NULL && connection != NULL &&
   key != NULL && version != NULL &&
   mg_strcasestr(upgrade, "websocket") != NULL &&
   mg_strcasestr(connection, "Upgrade") != NULL;
}
#endif // !USE_WEBSOCKET

static int isbyte(int n) {
   return n >= 0 && n <= 255;
}

static int parse_net(const char *spec, uint32_t *net, uint32_t *mask) {
   int n, a, b, c, d, slash = 32, len = 0;
   
   if ((sscanf(spec, "%d.%d.%d.%d/%d%n", &a, &b, &c, &d, &slash, &n) == 5 ||
        sscanf(spec, "%d.%d.%d.%d%n", &a, &b, &c, &d, &n) == 4) &&
       isbyte(a) && isbyte(b) && isbyte(c) && isbyte(d) &&
       slash >= 0 && slash < 33) {
      len = n;
      *net = ((uint32_t)a << 24) | ((uint32_t)b << 16) | ((uint32_t)c << 8) | d;
      *mask = slash ? 0xffffffffU << (32 - slash) : 0;
   }
   
   return len;
}

static int set_throttle(const char *spec, uint32_t remote_ip, const char *uri) {
   int throttle = 0;
   struct vec vec, val;
   uint32_t net, mask;
   char mult;
   double v;
   
   while ((spec = next_option(spec, &vec, &val)) != NULL) {
      mult = ',';
      if (sscanf(val.ptr, "%lf%c", &v, &mult) < 1 || v < 0 ||
          (lowercase(&mult) != 'k' && lowercase(&mult) != 'm' && mult != ',')) {
         continue;
      }
      v *= lowercase(&mult) == 'k' ? 1024 : lowercase(&mult) == 'm' ? 1048576 : 1;
      if (vec.len == 1 && vec.ptr[0] == '*') {
         throttle = (int) v;
      } else if (parse_net(vec.ptr, &net, &mask) > 0) {
         if ((remote_ip & mask) == net) {
            throttle = (int) v;
         }
      } else if (match_prefix(vec.ptr, vec.len, uri) > 0) {
         throttle = (int) v;
      }
   }
   
   return throttle;
}

static uint32_t get_remote_ip(const struct mg_connection *conn) {
   return ntohl(* (uint32_t *) &conn->client.rsa.sin.sin_addr);
}

#ifdef USE_LUA
#include "mod_lua.c"
#endif // USE_LUA

int mg_upload(struct mg_connection *conn, const char *destination_dir) {
   const char *content_type_header, *boundary_start;
   char buf[MG_BUF_LEN], path[PATH_MAX], fname[1024], boundary[100], *s;
   FILE *fp;
   int bl, n, i, j, headers_len, boundary_len, eof,
   len = 0, num_uploaded_files = 0;
   
   // Request looks like this:
   //
   // POST /upload HTTP/1.1
   // Host: 127.0.0.1:8080
   // Content-Length: 244894
   // Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryRVr
   //
   // ------WebKitFormBoundaryRVr
   // Content-Disposition: form-data; name="file"; filename="accum.png"
   // Content-Type: image/png
   //
   //  <89>PNG
   //  <PNG DATA>
   // ------WebKitFormBoundaryRVr
   
   // Extract boundary string from the Content-Type header
   if ((content_type_header = mg_get_header(conn, "Content-Type")) == NULL ||
       (boundary_start = mg_strcasestr(content_type_header,
                                       "boundary=")) == NULL ||
       (sscanf(boundary_start, "boundary=\"%99[^\"]\"", boundary) == 0 &&
        sscanf(boundary_start, "boundary=%99s", boundary) == 0) ||
       boundary[0] == '\0') {
      return num_uploaded_files;
   }
   
   boundary_len = strlen(boundary);
   bl = boundary_len + 4;  // \r\n--<boundary>
   for (;;) {
      // Pull in headers
      assert(len >= 0 && len <= (int) sizeof(buf));
      while ((n = mg_read(conn, buf + len, sizeof(buf) - len)) > 0) {
         len += n;
      }
      if ((headers_len = get_request_len(buf, len)) <= 0) {
         break;
      }
      
      // Fetch file name.
      fname[0] = '\0';
      for (i = j = 0; i < headers_len; i++) {
         if (buf[i] == '\r' && buf[i + 1] == '\n') {
            buf[i] = buf[i + 1] = '\0';
            // TODO(lsm): don't expect filename to be the 3rd field,
            // parse the header properly instead.
            sscanf(&buf[j], "Content-Disposition: %*s %*s filename=\"%1023[^\"]",
                   fname);
            j = i + 2;
         }
      }
      
      // Give up if the headers are not what we expect
      if (fname[0] == '\0') {
         break;
      }
      
      // Move data to the beginning of the buffer
      assert(len >= headers_len);
      memmove(buf, &buf[headers_len], len - headers_len);
      len -= headers_len;
      
      // We open the file with exclusive lock held. This guarantee us
      // there is no other thread can save into the same file simultaneously.
      fp = NULL;
      // Construct destination file name. Do not allow paths to have slashes.
      if ((s = strrchr(fname, '/')) == NULL) {
         s = fname;
      }
      // Open file in binary mode. TODO: set an exclusive lock.
      snprintf(path, sizeof(path), "%s/%s", destination_dir, s);
      if ((fp = fopen(path, "wb")) == NULL) {
         break;
      }
      
      // Read POST data, write into file until boundary is found.
      eof = n = 0;
      do {
         len += n;
         for (i = 0; i < len - bl; i++) {
            if (!memcmp(&buf[i], "\r\n--", 4) &&
                !memcmp(&buf[i + 4], boundary, boundary_len)) {
               // Found boundary, that's the end of file data.
               fwrite(buf, 1, i, fp);
               eof = 1;
               memmove(buf, &buf[i + bl], len - (i + bl));
               len -= i + bl;
               break;
            }
         }
         if (!eof && len > bl) {
            fwrite(buf, 1, len - bl, fp);
            memmove(buf, &buf[len - bl], bl);
            len = bl;
         }
      } while (!eof && (n = mg_read(conn, buf + len, sizeof(buf) - len)) > 0);
      fclose(fp);
      if (eof) {
         num_uploaded_files++;
         if (conn->ctx->callbacks.upload != NULL) {
            conn->ctx->callbacks.upload(conn, path);
         }
      }
   }
   
   return num_uploaded_files;
}

static int is_put_or_delete_request(const struct mg_connection *conn) {
   const char *s = conn->request_info.request_method;
   return s != NULL && (!strcmp(s, "PUT") || !strcmp(s, "DELETE"));
}

static int get_first_ssl_listener_index(const struct mg_context *ctx) {
   int i, index = -1;
   for (i = 0; index == -1 && i < ctx->num_listening_sockets; i++) {
      index = ctx->listening_sockets[i].is_ssl ? i : -1;
   }
   return index;
}

static void redirect_to_https_port(struct mg_connection *conn, int ssl_index) {
   char host[1025];
   const char *host_header;
   
   if ((host_header = mg_get_header(conn, "Host")) == NULL ||
       sscanf(host_header, "%1024[^:]", host) == 0) {
      // Cannot get host from the Host: header. Fallback to our IP address.
      sockaddr_to_string(host, sizeof(host), &conn->client.lsa);
   }
   
   mg_printf(conn, "HTTP/1.1 302 Found\r\nLocation: https://%s:%d%s\r\n\r\n",
             host, (int) ntohs(conn->ctx->listening_sockets[ssl_index].
                               lsa.sin.sin_port), conn->request_info.uri);
}

// This is the heart of the Mongoose's logic.
// This function is called when the request is read, parsed and validated,
// and Mongoose must decide what action to take: serve a file, or
// a directory, or call embedded function, etcetera.
static void handle_request(struct mg_connection *conn) {
   struct mg_request_info *ri = &conn->request_info;
   char path[PATH_MAX];
   int uri_len, ssl_index;
   struct file file = STRUCT_FILE_INITIALIZER;
   
   if ((conn->request_info.query_string = strchr(ri->uri, '?')) != NULL) {
      * ((char *) conn->request_info.query_string++) = '\0';
   }
   uri_len = (int) strlen(ri->uri);
   mg_url_decode(ri->uri, uri_len, (char *) ri->uri, uri_len + 1, 0);
   remove_double_dots_and_double_slashes((char *) ri->uri);
   convert_uri_to_file_name(conn, path, sizeof(path), &file);
   conn->throttle = set_throttle(conn->ctx->config[THROTTLE],
                                 get_remote_ip(conn), ri->uri);
   
   DEBUG_TRACE(("%s", ri->uri));
   // Perform redirect and auth checks before calling begin_request() handler.
   // Otherwise, begin_request() would need to perform auth checks and redirects.
   if (!conn->client.is_ssl && conn->client.ssl_redir &&
       (ssl_index = get_first_ssl_listener_index(conn->ctx)) > -1) {
      redirect_to_https_port(conn, ssl_index);
   } else if (!is_put_or_delete_request(conn) &&
              !check_authorization(conn, path)) {
      send_authorization_request(conn);
   } else if (conn->ctx->callbacks.begin_request != NULL &&
              conn->ctx->callbacks.begin_request(conn)) {
      // Do nothing, callback has served the request
#if defined(USE_WEBSOCKET)
   } else if (is_websocket_request(conn)) {
      handle_websocket_request(conn);
#endif
   } else if (!strcmp(ri->request_method, "OPTIONS")) {
      send_options(conn);
   } else if (conn->ctx->config[DOCUMENT_ROOT] == NULL) {
      send_http_error(conn, 404, "Not Found", "Not Found");
   } else if (is_put_or_delete_request(conn) &&
              (conn->ctx->config[PUT_DELETE_PASSWORDS_FILE] == NULL ||
               is_authorized_for_put(conn) != 1)) {
                 send_authorization_request(conn);
              } else if (!strcmp(ri->request_method, "PUT")) {
                 put_file(conn, path);
              } else if (!strcmp(ri->request_method, "DELETE")) {
                 if (mg_remove(path) == 0) {
                    send_http_error(conn, 200, "OK", "%s", "");
                 } else {
                    send_http_error(conn, 500, http_500_error, "remove(%s): %s", path,
                                    strerror(ERRNO));
                 }
              } else if ((file.membuf == NULL && file.modification_time == (time_t) 0) ||
                         must_hide_file(conn, path)) {
                 send_http_error(conn, 404, "Not Found", "%s", "File not found");
              } else if (file.is_directory && ri->uri[uri_len - 1] != '/') {
                 mg_printf(conn, "HTTP/1.1 301 Moved Permanently\r\n"
                           "Location: %s/\r\n\r\n", ri->uri);
              } else if (!strcmp(ri->request_method, "PROPFIND")) {
                 handle_propfind(conn, path, &file);
              } else if (file.is_directory &&
                         !substitute_index_file(conn, path, sizeof(path), &file)) {
                 if (!mg_strcasecmp(conn->ctx->config[ENABLE_DIRECTORY_LISTING], "yes")) {
                    handle_directory_request(conn, path);
                 } else {
                    send_http_error(conn, 403, "Directory Listing Denied",
                                    "Directory listing denied");
                 }
#ifdef USE_LUA
              } else if (match_prefix("**.lp$", 6, path) > 0) {
                 handle_lsp_request(conn, path, &file, NULL);
#endif
#if !defined(NO_CGI)
              } else if (match_prefix(conn->ctx->config[CGI_EXTENSIONS],
                                      strlen(conn->ctx->config[CGI_EXTENSIONS]),
                                      path) > 0) {
                 if (strcmp(ri->request_method, "POST") &&
                     strcmp(ri->request_method, "HEAD") &&
                     strcmp(ri->request_method, "GET")) {
                    send_http_error(conn, 501, "Not Implemented",
                                    "Method %s is not implemented", ri->request_method);
                 } else {
                    handle_cgi_request(conn, path);
                 }
#endif // !NO_CGI
              } else if (match_prefix(conn->ctx->config[SSI_EXTENSIONS],
                                      strlen(conn->ctx->config[SSI_EXTENSIONS]),
                                      path) > 0) {
                 handle_ssi_file_request(conn, path);
              } else if (is_not_modified(conn, &file)) {
                 send_http_error(conn, 304, "Not Modified", "%s", "");
              } else {
                 handle_file_request(conn, path, &file);
              }
}

static void close_all_listening_sockets(struct mg_context *ctx) {
   int i;
   for (i = 0; i < ctx->num_listening_sockets; i++) {
      closesocket(ctx->listening_sockets[i].sock);
   }
   free(ctx->listening_sockets);
}

// Valid listening port specification is: [ip_address:]port[s]
// Examples: 80, 443s, 127.0.0.1:3128, 1.2.3.4:8080s
// TODO(lsm): add parsing of the IPv6 address
static int parse_port_string(const struct vec *vec, struct socket *so) {
   int a, b, c, d, port, len;
   
   // MacOS needs that. If we do not zero it, subsequent bind() will fail.
   // Also, all-zeroes in the socket address means binding to all addresses
   // for both IPv4 and IPv6 (INADDR_ANY and IN6ADDR_ANY_INIT).
   memset(so, 0, sizeof(*so));
   
   if (sscanf(vec->ptr, "%d.%d.%d.%d:%d%n", &a, &b, &c, &d, &port, &len) == 5) {
      // Bind to a specific IPv4 address
      so->lsa.sin.sin_addr.s_addr = htonl((a << 24) | (b << 16) | (c << 8) | d);
   } else if (sscanf(vec->ptr, "%d%n", &port, &len) != 1 ||
              len <= 0 ||
              len > (int) vec->len ||
              port < 1 ||
              port > 65535 ||
              (vec->ptr[len] && vec->ptr[len] != 's' &&
               vec->ptr[len] != 'r' && vec->ptr[len] != ',')) {
                 return 0;
              }
   
   so->is_ssl = vec->ptr[len] == 's';
   so->ssl_redir = vec->ptr[len] == 'r';
#if defined(USE_IPV6)
   so->lsa.sin6.sin6_family = AF_INET6;
   so->lsa.sin6.sin6_port = htons((uint16_t) port);
#else
   so->lsa.sin.sin_family = AF_INET;
   so->lsa.sin.sin_port = htons((uint16_t) port);
#endif
   
   return 1;
}

static int set_ports_option(struct mg_context *ctx) {
   const char *list = ctx->config[LISTENING_PORTS];
   int on = 1, success = 1;
#if defined(USE_IPV6)
   int off = 0;
#endif
   struct vec vec;
   struct socket so, *ptr;
   
   while (success && (list = next_option(list, &vec, NULL)) != NULL) {
      if (!parse_port_string(&vec, &so)) {
         cry(fc(ctx), "%s: %.*s: invalid port spec. Expecting list of: %s",
             __func__, (int) vec.len, vec.ptr, "[IP_ADDRESS:]PORT[s|p]");
         success = 0;
      } else if (so.is_ssl && ctx->ssl_ctx == NULL) {
         cry(fc(ctx), "Cannot add SSL socket, is -ssl_certificate option set?");
         success = 0;
      } else if ((so.sock = socket(so.lsa.sa.sa_family, SOCK_STREAM, 6)) ==
                 INVALID_SOCKET ||
                 // On Windows, SO_REUSEADDR is recommended only for
                 // broadcast UDP sockets
                 setsockopt(so.sock, SOL_SOCKET, SO_REUSEADDR,
                            (void *) &on, sizeof(on)) != 0 ||
#if defined(USE_IPV6)
                 setsockopt(so.sock, IPPROTO_IPV6, IPV6_V6ONLY, (void *) &off,
                            sizeof(off)) != 0 ||
#endif
                 bind(so.sock, &so.lsa.sa, sizeof(so.lsa)) != 0 ||
                 listen(so.sock, SOMAXCONN) != 0) {
         cry(fc(ctx), "%s: cannot bind to %.*s: %s", __func__,
             (int) vec.len, vec.ptr, strerror(ERRNO));
         closesocket(so.sock);
         success = 0;
      } else if ((ptr = realloc(ctx->listening_sockets,
                                (ctx->num_listening_sockets + 1) *
                                sizeof(ctx->listening_sockets[0]))) == NULL) {
         closesocket(so.sock);
         success = 0;
      } else {
         set_close_on_exec(so.sock);
         ctx->listening_sockets = ptr;
         ctx->listening_sockets[ctx->num_listening_sockets] = so;
         ctx->num_listening_sockets++;
      }
   }
   
   if (!success) {
      close_all_listening_sockets(ctx);
   }
   
   return success;
}

static void log_header(const struct mg_connection *conn, const char *header,
                       FILE *fp) {
   const char *header_value;
   
   if ((header_value = mg_get_header(conn, header)) == NULL) {
      (void) fprintf(fp, "%s", " -");
   } else {
      (void) fprintf(fp, " \"%s\"", header_value);
   }
}

static void log_access(const struct mg_connection *conn) {
   const struct mg_request_info *ri;
   FILE *fp;
   char date[64], src_addr[20];
   
   fp = conn->ctx->config[ACCESS_LOG_FILE] == NULL ?  NULL :
   fopen(conn->ctx->config[ACCESS_LOG_FILE], "a+");
   
   if (fp == NULL)
      return;
   
   strftime(date, sizeof(date), "%d/%b/%Y:%H:%M:%S %z",
            localtime(&conn->birth_time));
   
   ri = &conn->request_info;
   flockfile(fp);
   
   sockaddr_to_string(src_addr, sizeof(src_addr), &conn->client.rsa);
   fprintf(fp, "%s - %s [%s] \"%s %s HTTP/%s\" %d %" INT64_FMT,
           src_addr, ri->remote_user == NULL ? "-" : ri->remote_user, date,
           ri->request_method ? ri->request_method : "-",
           ri->uri ? ri->uri : "-", ri->http_version,
           conn->status_code, conn->num_bytes_sent);
   log_header(conn, "Referer", fp);
   log_header(conn, "User-Agent", fp);
   fputc('\n', fp);
   fflush(fp);
   
   funlockfile(fp);
   fclose(fp);
}

// Verify given socket address against the ACL.
// Return -1 if ACL is malformed, 0 if address is disallowed, 1 if allowed.
static int check_acl(struct mg_context *ctx, uint32_t remote_ip) {
   int allowed, flag;
   uint32_t net, mask;
   struct vec vec;
   const char *list = ctx->config[ACCESS_CONTROL_LIST];
   
   // If any ACL is set, deny by default
   allowed = list == NULL ? '+' : '-';
   
   while ((list = next_option(list, &vec, NULL)) != NULL) {
      flag = vec.ptr[0];
      if ((flag != '+' && flag != '-') ||
          parse_net(&vec.ptr[1], &net, &mask) == 0) {
         cry(fc(ctx), "%s: subnet must be [+|-]x.x.x.x[/x]", __func__);
         return -1;
      }
      
      if (net == (remote_ip & mask)) {
         allowed = flag;
      }
   }
   
   return allowed == '+';
}

#if !defined(_WIN32)
static int set_uid_option(struct mg_context *ctx) {
   struct passwd *pw;
   const char *uid = ctx->config[RUN_AS_USER];
   int success = 0;
   
   if (uid == NULL) {
      success = 1;
   } else {
      if ((pw = getpwnam(uid)) == NULL) {
         cry(fc(ctx), "%s: unknown user [%s]", __func__, uid);
      } else if (setgid(pw->pw_gid) == -1) {
         cry(fc(ctx), "%s: setgid(%s): %s", __func__, uid, strerror(errno));
      } else if (setuid(pw->pw_uid) == -1) {
         cry(fc(ctx), "%s: setuid(%s): %s", __func__, uid, strerror(errno));
      } else {
         success = 1;
      }
   }
   
   return success;
}
#endif // !_WIN32

#if !defined(NO_SSL)
static pthread_mutex_t *ssl_mutexes;

static int sslize(struct mg_connection *conn, SSL_CTX *s, int (*func)(SSL *)) {
   return (conn->ssl = SSL_new(s)) != NULL &&
   SSL_set_fd(conn->ssl, conn->client.sock) == 1 &&
   func(conn->ssl) == 1;
}

// Return OpenSSL error message
static const char *ssl_error(void) {
   unsigned long err;
   err = ERR_get_error();
   return err == 0 ? "" : ERR_error_string(err, NULL);
}

static void ssl_locking_callback(int mode, int mutex_num, const char *file,
                                 int line) {
   (void) line;
   (void) file;
   
   if (mode & 1) {  // 1 is CRYPTO_LOCK
      (void) pthread_mutex_lock(&ssl_mutexes[mutex_num]);
   } else {
      (void) pthread_mutex_unlock(&ssl_mutexes[mutex_num]);
   }
}

static unsigned long ssl_id_callback(void) {
   return (unsigned long) pthread_self();
}

#if !defined(NO_SSL_DL)
static int load_dll(struct mg_context *ctx, const char *dll_name,
                    struct ssl_func *sw) {
   union {void *p; void (*fp)(void);} u;
   void  *dll_handle;
   struct ssl_func *fp;
   
   if ((dll_handle = dlopen(dll_name, RTLD_LAZY)) == NULL) {
      cry(fc(ctx), "%s: cannot load %s", __func__, dll_name);
      return 0;
   }
   
   for (fp = sw; fp->name != NULL; fp++) {
#ifdef _WIN32
      // GetProcAddress() returns pointer to function
      u.fp = (void (*)(void)) dlsym(dll_handle, fp->name);
#else
      // dlsym() on UNIX returns void *. ISO C forbids casts of data pointers to
      // function pointers. We need to use a union to make a cast.
      u.p = dlsym(dll_handle, fp->name);
#endif // _WIN32
      if (u.fp == NULL) {
         cry(fc(ctx), "%s: %s: cannot find %s", __func__, dll_name, fp->name);
         return 0;
      } else {
         fp->ptr = u.fp;
      }
   }
   
   return 1;
}
#endif // NO_SSL_DL

// Dynamically load SSL library. Set up ctx->ssl_ctx pointer.
static int set_ssl_option(struct mg_context *ctx) {
   int i, size;
   const char *pem;
   
   // If PEM file is not specified, skip SSL initialization.
   if ((pem = ctx->config[SSL_CERTIFICATE]) == NULL) {
      return 1;
   }
   
#if !defined(NO_SSL_DL)
   if (!load_dll(ctx, SSL_LIB, ssl_sw) ||
       !load_dll(ctx, CRYPTO_LIB, crypto_sw)) {
      return 0;
   }
#endif // NO_SSL_DL
   
   // Initialize SSL library
   SSL_library_init();
   SSL_load_error_strings();
   
   if ((ctx->ssl_ctx = SSL_CTX_new(SSLv23_server_method())) == NULL) {
      cry(fc(ctx), "SSL_CTX_new (server) error: %s", ssl_error());
      return 0;
   }
   
   // If user callback returned non-NULL, that means that user callback has
   // set up certificate itself. In this case, skip sertificate setting.
   if ((ctx->callbacks.init_ssl == NULL ||
        !ctx->callbacks.init_ssl(ctx->ssl_ctx, ctx->user_data)) &&
       (SSL_CTX_use_certificate_file(ctx->ssl_ctx, pem, 1) == 0 ||
        SSL_CTX_use_PrivateKey_file(ctx->ssl_ctx, pem, 1) == 0)) {
          cry(fc(ctx), "%s: cannot open %s: %s", __func__, pem, ssl_error());
          return 0;
       }
   
   if (pem != NULL) {
      (void) SSL_CTX_use_certificate_chain_file(ctx->ssl_ctx, pem);
   }
   
   // Initialize locking callbacks, needed for thread safety.
   // http://www.openssl.org/support/faq.html#PROG1
   size = sizeof(pthread_mutex_t) * CRYPTO_num_locks();
   if ((ssl_mutexes = (pthread_mutex_t *) malloc((size_t)size)) == NULL) {
      cry(fc(ctx), "%s: cannot allocate mutexes: %s", __func__, ssl_error());
      return 0;
   }
   
   for (i = 0; i < CRYPTO_num_locks(); i++) {
      pthread_mutex_init(&ssl_mutexes[i], NULL);
   }
   
   CRYPTO_set_locking_callback(&ssl_locking_callback);
   CRYPTO_set_id_callback(&ssl_id_callback);
   
   return 1;
}

static void uninitialize_ssl(struct mg_context *ctx) {
   int i;
   if (ctx->ssl_ctx != NULL) {
      CRYPTO_set_locking_callback(NULL);
      for (i = 0; i < CRYPTO_num_locks(); i++) {
         pthread_mutex_destroy(&ssl_mutexes[i]);
      }
      CRYPTO_set_locking_callback(NULL);
      CRYPTO_set_id_callback(NULL);
   }
}
#endif // !NO_SSL

static int set_gpass_option(struct mg_context *ctx) {
   struct file file = STRUCT_FILE_INITIALIZER;
   const char *path = ctx->config[GLOBAL_PASSWORDS_FILE];
   if (path != NULL && !mg_stat(fc(ctx), path, &file)) {
      cry(fc(ctx), "Cannot open %s: %s", path, strerror(ERRNO));
      return 0;
   }
   return 1;
}

static int set_acl_option(struct mg_context *ctx) {
   return check_acl(ctx, (uint32_t) 0x7f000001UL) != -1;
}

static void reset_per_request_attributes(struct mg_connection *conn) {
   conn->path_info = NULL;
   conn->num_bytes_sent = conn->consumed_content = 0;
   conn->status_code = -1;
   conn->must_close = conn->request_len = conn->throttle = 0;
}

static void close_socket_gracefully(struct mg_connection *conn) {
#if defined(_WIN32)
   char buf[MG_BUF_LEN];
   int n;
#endif
   struct linger linger;
   
   // Set linger option to avoid socket hanging out after close. This prevent
   // ephemeral port exhaust problem under high QPS.
   linger.l_onoff = 1;
   linger.l_linger = 1;
   setsockopt(conn->client.sock, SOL_SOCKET, SO_LINGER,
              (char *) &linger, sizeof(linger));
   
   // Send FIN to the client
   shutdown(conn->client.sock, SHUT_WR);
   set_non_blocking_mode(conn->client.sock);
   
#if defined(_WIN32)
   // Read and discard pending incoming data. If we do not do that and close the
   // socket, the data in the send buffer may be discarded. This
   // behaviour is seen on Windows, when client keeps sending data
   // when server decides to close the connection; then when client
   // does recv() it gets no data back.
   do {
      n = pull(NULL, conn, buf, sizeof(buf));
   } while (n > 0);
#endif
   
   // Now we know that our FIN is ACK-ed, safe to close
   closesocket(conn->client.sock);
}

static void close_connection(struct mg_connection *conn) {
   conn->must_close = 1;
   
#ifndef NO_SSL
   if (conn->ssl != NULL) {
      // Run SSL_shutdown twice to ensure completly close SSL connection
      SSL_shutdown(conn->ssl);
      SSL_shutdown(conn->ssl);
      SSL_free(conn->ssl);
      conn->ssl = NULL;
   }
#endif
   if (conn->client.sock != INVALID_SOCKET) {
      close_socket_gracefully(conn);
      conn->client.sock = INVALID_SOCKET;
   }
}

void mg_close_connection(struct mg_connection *conn) {
#ifndef NO_SSL
   if (conn->client_ssl_ctx != NULL) {
      SSL_CTX_free((SSL_CTX *) conn->client_ssl_ctx);
   }
#endif
   close_connection(conn);
   free(conn);
}

struct mg_connection *mg_connect(const char *host, int port, int use_ssl,
                                 char *ebuf, size_t ebuf_len) {
   static struct mg_context fake_ctx;
   struct mg_connection *conn = NULL;
   SOCKET sock;
   
   if ((sock = conn2(host, port, use_ssl, ebuf, ebuf_len)) == INVALID_SOCKET) {
   } else if ((conn = (struct mg_connection *)
               calloc(1, sizeof(*conn) + MAX_REQUEST_SIZE)) == NULL) {
      snprintf(ebuf, ebuf_len, "calloc(): %s", strerror(ERRNO));
      closesocket(sock);
#ifndef NO_SSL
   } else if (use_ssl && (conn->client_ssl_ctx =
                          SSL_CTX_new(SSLv23_client_method())) == NULL) {
      snprintf(ebuf, ebuf_len, "SSL_CTX_new error");
      closesocket(sock);
      free(conn);
      conn = NULL;
#endif // NO_SSL
   } else {
      socklen_t len;
      conn->buf_size = MAX_REQUEST_SIZE;
      conn->buf = (char *) (conn + 1);
      conn->ctx = &fake_ctx;
      conn->client.sock = sock;
      getsockname(sock, &conn->client.rsa.sa, &len);
      conn->client.is_ssl = use_ssl;
#ifndef NO_SSL
      if (use_ssl) {
         // SSL_CTX_set_verify call is needed to switch off server certificate
         // checking, which is off by default in OpenSSL and on in yaSSL.
         SSL_CTX_set_verify(conn->client_ssl_ctx, 0, 0);
         sslize(conn, conn->client_ssl_ctx, SSL_connect);
      }
#endif
   }
   
   return conn;
}

static int is_valid_uri(const char *uri) {
   // Conform to http://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html#sec5.1.2
   // URI can be an asterisk (*) or should start with slash.
   return uri[0] == '/' || (uri[0] == '*' && uri[1] == '\0');
}

static int getreq(struct mg_connection *conn, char *ebuf, size_t ebuf_len) {
   const char *cl;
   
   ebuf[0] = '\0';
   reset_per_request_attributes(conn);
   conn->request_len = read_request(NULL, conn, conn->buf, conn->buf_size,
                                    &conn->data_len);
   assert(conn->request_len < 0 || conn->data_len >= conn->request_len);
   
   if (conn->request_len == 0 && conn->data_len == conn->buf_size) {
      snprintf(ebuf, ebuf_len, "%s", "Request Too Large");
   } else if (conn->request_len <= 0) {
      snprintf(ebuf, ebuf_len, "%s", "Client closed connection");
   } else if (parse_http_message(conn->buf, conn->buf_size,
                                 &conn->request_info) <= 0) {
      snprintf(ebuf, ebuf_len, "Bad request: [%.*s]", conn->data_len, conn->buf);
   } else {
      // Request is valid
      if ((cl = get_header(&conn->request_info, "Content-Length")) != NULL) {
         conn->content_len = strtoll(cl, NULL, 10);
      } else if (!mg_strcasecmp(conn->request_info.request_method, "POST") ||
                 !mg_strcasecmp(conn->request_info.request_method, "PUT")) {
         conn->content_len = -1;
      } else {
         conn->content_len = 0;
      }
      conn->birth_time = time(NULL);
   }
   return ebuf[0] == '\0';
}

struct mg_connection *mg_download(const char *host, int port, int use_ssl,
                                  char *ebuf, size_t ebuf_len,
                                  const char *fmt, ...) {
   struct mg_connection *conn;
   va_list ap;
   
   va_start(ap, fmt);
   ebuf[0] = '\0';
   if ((conn = mg_connect(host, port, use_ssl, ebuf, ebuf_len)) == NULL) {
   } else if (mg_vprintf(conn, fmt, ap) <= 0) {
      snprintf(ebuf, ebuf_len, "%s", "Error sending request");
   } else {
      getreq(conn, ebuf, ebuf_len);
   }
   if (ebuf[0] != '\0' && conn != NULL) {
      mg_close_connection(conn);
      conn = NULL;
   }
   
   return conn;
}

static void process_new_connection(struct mg_connection *conn) {
   struct mg_request_info *ri = &conn->request_info;
   int keep_alive_enabled, keep_alive, discard_len;
   char ebuf[100];
   
   keep_alive_enabled = !strcmp(conn->ctx->config[ENABLE_KEEP_ALIVE], "yes");
   keep_alive = 0;
   
   // Important: on new connection, reset the receiving buffer. Credit goes
   // to crule42.
   conn->data_len = 0;
   do {
      if (!getreq(conn, ebuf, sizeof(ebuf))) {
         send_http_error(conn, 500, "Server Error", "%s", ebuf);
         conn->must_close = 1;
      } else if (!is_valid_uri(conn->request_info.uri)) {
         snprintf(ebuf, sizeof(ebuf), "Invalid URI: [%s]", ri->uri);
         send_http_error(conn, 400, "Bad Request", "%s", ebuf);
      } else if (strcmp(ri->http_version, "1.0") &&
                 strcmp(ri->http_version, "1.1")) {
         snprintf(ebuf, sizeof(ebuf), "Bad HTTP version: [%s]", ri->http_version);
         send_http_error(conn, 505, "Bad HTTP version", "%s", ebuf);
      }
      
      if (ebuf[0] == '\0') {
         handle_request(conn);
         if (conn->ctx->callbacks.end_request != NULL) {
            conn->ctx->callbacks.end_request(conn, conn->status_code);
         }
         log_access(conn);
      }
      if (ri->remote_user != NULL) {
         free((void *) ri->remote_user);
         ri->remote_user = NULL; // when having connections with and without auth would cause double free and then crash
      }
      
      // NOTE(lsm): order is important here. should_keep_alive() call
      // is using parsed request, which will be invalid after memmove's below.
      // Therefore, memorize should_keep_alive() result now for later use
      // in loop exit condition.
      keep_alive = conn->ctx->stop_flag == 0 && keep_alive_enabled &&
      conn->content_len >= 0 && should_keep_alive(conn);
      
      // Discard all buffered data for this request
      discard_len = conn->content_len >= 0 && conn->request_len > 0 &&
      conn->request_len + conn->content_len < (int64_t) conn->data_len ?
      (int) (conn->request_len + conn->content_len) : conn->data_len;
      assert(discard_len >= 0);
      memmove(conn->buf, conn->buf + discard_len, conn->data_len - discard_len);
      conn->data_len -= discard_len;
      assert(conn->data_len >= 0);
      assert(conn->data_len <= conn->buf_size);
   } while (keep_alive);
}

// Worker threads take accepted socket from the queue
static int consume_socket(struct mg_context *ctx, struct socket *sp) {
   (void) pthread_mutex_lock(&ctx->mutex);
   DEBUG_TRACE(("going idle"));
   
   // If the queue is empty, wait. We're idle at this point.
   while (ctx->sq_head == ctx->sq_tail && ctx->stop_flag == 0) {
      pthread_cond_wait(&ctx->sq_full, &ctx->mutex);
   }
   
   // If we're stopping, sq_head may be equal to sq_tail.
   if (ctx->sq_head > ctx->sq_tail) {
      // Copy socket from the queue and increment tail
      *sp = ctx->queue[ctx->sq_tail % ARRAY_SIZE(ctx->queue)];
      ctx->sq_tail++;
      DEBUG_TRACE(("grabbed socket %d, going busy", sp->sock));
      
      // Wrap pointers if needed
      while (ctx->sq_tail > (int) ARRAY_SIZE(ctx->queue)) {
         ctx->sq_tail -= ARRAY_SIZE(ctx->queue);
         ctx->sq_head -= ARRAY_SIZE(ctx->queue);
      }
   }
   
   (void) pthread_cond_signal(&ctx->sq_empty);
   (void) pthread_mutex_unlock(&ctx->mutex);
   
   return !ctx->stop_flag;
}

static void *worker_thread(void *thread_func_param) {
   struct mg_context *ctx = thread_func_param;
   struct mg_connection *conn;
   
   conn = (struct mg_connection *) calloc(1, sizeof(*conn) + MAX_REQUEST_SIZE);
   if (conn == NULL) {
      cry(fc(ctx), "%s", "Cannot create new connection struct, OOM");
   } else {
      conn->buf_size = MAX_REQUEST_SIZE;
      conn->buf = (char *) (conn + 1);
      conn->ctx = ctx;
      conn->request_info.user_data = ctx->user_data;
      
      // Call consume_socket() even when ctx->stop_flag > 0, to let it signal
      // sq_empty condvar to wake up the master waiting in produce_socket()
      while (consume_socket(ctx, &conn->client)) {
         conn->birth_time = time(NULL);
         
         // Fill in IP, port info early so even if SSL setup below fails,
         // error handler would have the corresponding info.
         // Thanks to Johannes Winkelmann for the patch.
         // TODO(lsm): Fix IPv6 case
         conn->request_info.remote_port = ntohs(conn->client.rsa.sin.sin_port);
         memcpy(&conn->request_info.remote_ip,
                &conn->client.rsa.sin.sin_addr.s_addr, 4);
         conn->request_info.remote_ip = ntohl(conn->request_info.remote_ip);
         conn->request_info.is_ssl = conn->client.is_ssl;
         
         if (!conn->client.is_ssl
#ifndef NO_SSL
             || sslize(conn, conn->ctx->ssl_ctx, SSL_accept)
#endif
             ) {
            process_new_connection(conn);
         }
         
         close_connection(conn);
      }
      free(conn);
   }
   
   // Signal master that we're done with connection and exiting
   (void) pthread_mutex_lock(&ctx->mutex);
   ctx->num_threads--;
   (void) pthread_cond_signal(&ctx->cond);
   assert(ctx->num_threads >= 0);
   (void) pthread_mutex_unlock(&ctx->mutex);
   
   DEBUG_TRACE(("exiting"));
   return NULL;
}

// Master thread adds accepted socket to a queue
static void produce_socket(struct mg_context *ctx, const struct socket *sp) {
   (void) pthread_mutex_lock(&ctx->mutex);
   
   // If the queue is full, wait
   while (ctx->stop_flag == 0 &&
          ctx->sq_head - ctx->sq_tail >= (int) ARRAY_SIZE(ctx->queue)) {
      (void) pthread_cond_wait(&ctx->sq_empty, &ctx->mutex);
   }
   
   if (ctx->sq_head - ctx->sq_tail < (int) ARRAY_SIZE(ctx->queue)) {
      // Copy socket to the queue and increment head
      ctx->queue[ctx->sq_head % ARRAY_SIZE(ctx->queue)] = *sp;
      ctx->sq_head++;
      DEBUG_TRACE(("queued socket %d", sp->sock));
   }
   
   (void) pthread_cond_signal(&ctx->sq_full);
   (void) pthread_mutex_unlock(&ctx->mutex);
}

static int set_sock_timeout(SOCKET sock, int milliseconds) {
#ifdef _WIN32
   DWORD t = milliseconds;
#else
   struct timeval t;
   t.tv_sec = milliseconds / 1000;
   t.tv_usec = (milliseconds * 1000) % 1000000;
#endif
   return setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, (void *) &t, sizeof(t)) ||
   setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, (void *) &t, sizeof(t));
}

static void accept_new_connection(const struct socket *listener,
                                  struct mg_context *ctx) {
   struct socket so;
   char src_addr[20];
   socklen_t len = sizeof(so.rsa);
   int on = 1;
   
   if ((so.sock = accept(listener->sock, &so.rsa.sa, &len)) == INVALID_SOCKET) {
   } else if (!check_acl(ctx, ntohl(* (uint32_t *) &so.rsa.sin.sin_addr))) {
      sockaddr_to_string(src_addr, sizeof(src_addr), &so.rsa);
      cry(fc(ctx), "%s: %s is not allowed to connect", __func__, src_addr);
      closesocket(so.sock);
   } else {
      // Put so socket structure into the queue
      DEBUG_TRACE(("Accepted socket %d", (int) so.sock));
      so.is_ssl = listener->is_ssl;
      so.ssl_redir = listener->ssl_redir;
      getsockname(so.sock, &so.lsa.sa, &len);
      // Set TCP keep-alive. This is needed because if HTTP-level keep-alive
      // is enabled, and client resets the connection, server won't get
      // TCP FIN or RST and will keep the connection open forever. With TCP
      // keep-alive, next keep-alive handshake will figure out that the client
      // is down and will close the server end.
      // Thanks to Igor Klopov who suggested the patch.
      setsockopt(so.sock, SOL_SOCKET, SO_KEEPALIVE, (void *) &on, sizeof(on));
      set_sock_timeout(so.sock, atoi(ctx->config[REQUEST_TIMEOUT]));
      produce_socket(ctx, &so);
   }
}

static void *master_thread(void *thread_func_param) {
   struct mg_context *ctx = thread_func_param;
   struct pollfd *pfd;
   int i;
   
   // Increase priority of the master thread
#if defined(_WIN32)
   SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_ABOVE_NORMAL);
#endif
   
#if defined(ISSUE_317)
   struct sched_param sched_param;
   sched_param.sched_priority = sched_get_priority_max(SCHED_RR);
   pthread_setschedparam(pthread_self(), SCHED_RR, &sched_param);
#endif
   
   pfd = calloc(ctx->num_listening_sockets, sizeof(pfd[0]));
   while (pfd != NULL && ctx->stop_flag == 0) {
      for (i = 0; i < ctx->num_listening_sockets; i++) {
         pfd[i].fd = ctx->listening_sockets[i].sock;
         pfd[i].events = POLLIN;
      }
      
      if (poll(pfd, ctx->num_listening_sockets, 200) > 0) {
         for (i = 0; i < ctx->num_listening_sockets; i++) {
            // NOTE(lsm): on QNX, poll() returns POLLRDNORM after the
            // successfull poll, and POLLIN is defined as (POLLRDNORM | POLLRDBAND)
            // Therefore, we're checking pfd[i].revents & POLLIN, not
            // pfd[i].revents == POLLIN.
            if (ctx->stop_flag == 0 && (pfd[i].revents & POLLIN)) {
               accept_new_connection(&ctx->listening_sockets[i], ctx);
            }
         }
      }
   }
   free(pfd);
   DEBUG_TRACE(("stopping workers"));
   
   // Stop signal received: somebody called mg_stop. Quit.
   close_all_listening_sockets(ctx);
   
   // Wakeup workers that are waiting for connections to handle.
   pthread_cond_broadcast(&ctx->sq_full);
   
   // Wait until all threads finish
   (void) pthread_mutex_lock(&ctx->mutex);
   while (ctx->num_threads > 0) {
      (void) pthread_cond_wait(&ctx->cond, &ctx->mutex);
   }
   (void) pthread_mutex_unlock(&ctx->mutex);
   
   // All threads exited, no sync is needed. Destroy mutex and condvars
   (void) pthread_mutex_destroy(&ctx->mutex);
   (void) pthread_cond_destroy(&ctx->cond);
   (void) pthread_cond_destroy(&ctx->sq_empty);
   (void) pthread_cond_destroy(&ctx->sq_full);
   
#if !defined(NO_SSL)
   uninitialize_ssl(ctx);
#endif
   DEBUG_TRACE(("exiting"));
   
   // Signal mg_stop() that we're done.
   // WARNING: This must be the very last thing this
   // thread does, as ctx becomes invalid after this line.
   ctx->stop_flag = 2;
   return NULL;
}

static void free_context(struct mg_context *ctx) {
   int i;
   
   // Deallocate config parameters
   for (i = 0; i < NUM_OPTIONS; i++) {
      if (ctx->config[i] != NULL)
         free(ctx->config[i]);
   }
   
#ifndef NO_SSL
   // Deallocate SSL context
   if (ctx->ssl_ctx != NULL) {
      SSL_CTX_free(ctx->ssl_ctx);
   }
   if (ssl_mutexes != NULL) {
      free(ssl_mutexes);
      ssl_mutexes = NULL;
   }
#endif // !NO_SSL
   
   // Deallocate context itself
   free(ctx);
   
}

void mg_stop(struct mg_context *ctx) {
   ctx->stop_flag = 1;
   
   // Wait until mg_fini() stops
   while (ctx->stop_flag != 2) {
      (void) mg_sleep(10);
   }
   free_context(ctx);
   
#if defined(_WIN32) && !defined(__SYMBIAN32__)
   (void) WSACleanup();
#endif // _WIN32
}

struct mg_context *mg_start(const struct mg_callbacks *callbacks,
                            void *user_data,
                            const char **options) {
   struct mg_context *ctx;
   const char *name, *value, *default_value;
   int i;
   
#if defined(_WIN32) && !defined(__SYMBIAN32__)
   WSADATA data;
   WSAStartup(MAKEWORD(2,2), &data);
   InitializeCriticalSection(&global_log_file_lock);
#endif // _WIN32
   
   // Allocate context and initialize reasonable general case defaults.
   // TODO(lsm): do proper error handling here.
   if ((ctx = (struct mg_context *) calloc(1, sizeof(*ctx))) == NULL) {
      return NULL;
   }
   ctx->callbacks = *callbacks;
   ctx->user_data = user_data;
   
   while (options && (name = *options++) != NULL) {
      if ((i = get_option_index(name)) == -1) {
         cry(fc(ctx), "Invalid option: %s", name);
         free_context(ctx);
         return NULL;
      } else if ((value = *options++) == NULL) {
         cry(fc(ctx), "%s: option value cannot be NULL", name);
         free_context(ctx);
         return NULL;
      }
      if (ctx->config[i] != NULL) {
         cry(fc(ctx), "warning: %s: duplicate option", name);
         free(ctx->config[i]);
      }
      ctx->config[i] = mg_strdup(value);
      DEBUG_TRACE(("[%s] -> [%s]", name, value));
   }
   
   // Set default value if needed
   for (i = 0; config_options[i * 2] != NULL; i++) {
      default_value = config_options[i * 2 + 1];
      if (ctx->config[i] == NULL && default_value != NULL) {
         ctx->config[i] = mg_strdup(default_value);
      }
   }
   
   // NOTE(lsm): order is important here. SSL certificates must
   // be initialized before listening ports. UID must be set last.
   if (!set_gpass_option(ctx) ||
#if !defined(NO_SSL)
       !set_ssl_option(ctx) ||
#endif
       !set_ports_option(ctx) ||
#if !defined(_WIN32)
       !set_uid_option(ctx) ||
#endif
       !set_acl_option(ctx)) {
      free_context(ctx);
      return NULL;
   }
   
#if !defined(_WIN32) && !defined(__SYMBIAN32__)
   // Ignore SIGPIPE signal, so if browser cancels the request, it
   // won't kill the whole process.
   (void) signal(SIGPIPE, SIG_IGN);
   // Also ignoring SIGCHLD to let the OS to reap zombies properly.
   (void) signal(SIGCHLD, SIG_IGN);
#endif // !_WIN32
   
   (void) pthread_mutex_init(&ctx->mutex, NULL);
   (void) pthread_cond_init(&ctx->cond, NULL);
   (void) pthread_cond_init(&ctx->sq_empty, NULL);
   (void) pthread_cond_init(&ctx->sq_full, NULL);
   
   // Start master (listening) thread
   mg_start_thread(master_thread, ctx);
   
   // Start worker threads
   for (i = 0; i < atoi(ctx->config[NUM_THREADS]); i++) {
      if (mg_start_thread(worker_thread, ctx) != 0) {
         cry(fc(ctx), "Cannot start worker thread: %ld", (long) ERRNO);
      } else {
         ctx->num_threads++;
      }
   }
   
   return ctx;
}
